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Motipally SI, Kolson DR, Guan T, Kolandaivelu S. Aberrant lipid accumulation and retinal pigment epithelium dysfunction in PRCD-deficient mice. Exp Eye Res 2024; 246:110016. [PMID: 39098587 PMCID: PMC11388538 DOI: 10.1016/j.exer.2024.110016] [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: 05/30/2024] [Revised: 07/24/2024] [Accepted: 07/30/2024] [Indexed: 08/06/2024]
Abstract
Progressive Rod-Cone Degeneration (PRCD) is an integral membrane protein found in photoreceptor outer segment (OS) disc membranes and its function remains unknown. Mutations in Prcd are implicated in Retinitis pigmentosa (RP) in humans and multiple dog breeds. PRCD-deficient models exhibit decreased levels of cholesterol in the plasma. However, potential changes in the retinal cholesterol remain unexplored. In addition, impaired phagocytosis observed in these animal models points to potential deficits in the retinal pigment epithelium (RPE). Here, using a Prcd-/- murine model we investigated the alterations in the retinal cholesterol levels and impairments in the structural and functional integrity of the RPE. Lipidomic and immunohistochemical analyses show a 5-fold increase in the levels of cholesteryl esters (C.Es) and lipid deposits in the PRCD-deficient retina, respectively, indicating alterations in total retinal cholesterol. Furthermore, the RPE of Prcd-/- mice exhibit a 1.7-fold increase in the expression of lipid transporter gene ATP-binding cassette transporter A1 (Abca1). Longitudinal fundus and spectral domain optical coherence tomography (SD-OCT) examinations showed focal lesions and RPE hyperreflectivity. Strikingly, the RPE of Prcd-/- mice exhibited age-related pathological features such as lipofuscin accumulation, Bruch's membrane (BrM) deposits and drusenoid focal deposits, mirroring an Age-related Macular Degeneration (AMD)-like phenotype. We propose that the extensive lipofuscin accumulation likely impairs lysosomal function, leading to the defective phagocytosis observed in Prcd-/- mice. Our findings support the dysregulation of retinal cholesterol homeostasis in the absence of PRCD. Further, we demonstrate that progressive photoreceptor degeneration in Prcd-/- mice is accompanied by progressive structural and functional deficits in the RPE, which likely exacerbates vision loss over time.
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Affiliation(s)
- Sree I Motipally
- Department of Neuroscience, Rockefeller Neuroscience Institute, 33 Medical Centre Drive, West Virginia University, Morgantown, WV, 26506, USA; Department of Ophthalmology and Visual Sciences, One Medical Center Drive, ERMA 2nd Floor, West Virginia University, Morgantown, WV, 26505-9193, USA
| | - Douglas R Kolson
- Department of Ophthalmology and Visual Sciences, One Medical Center Drive, ERMA 2nd Floor, West Virginia University, Morgantown, WV, 26505-9193, USA
| | - Tongju Guan
- Department of Ophthalmology and Visual Sciences, One Medical Center Drive, ERMA 2nd Floor, West Virginia University, Morgantown, WV, 26505-9193, USA; Department of Biochemistry and Molecular Medicine, 64 Medical Center Drive, West Virginia University, Morgantown, WV, 26505-9193, USA
| | - Saravanan Kolandaivelu
- Department of Ophthalmology and Visual Sciences, One Medical Center Drive, ERMA 2nd Floor, West Virginia University, Morgantown, WV, 26505-9193, USA; Department of Biochemistry and Molecular Medicine, 64 Medical Center Drive, West Virginia University, Morgantown, WV, 26505-9193, USA.
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2
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Motipally SI, Kolson DR, Guan T, Kolandaivelu S. Aberrant lipid accumulation and retinal pigmental epithelium dysfunction in PRCD-deficient mice. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.08.584131. [PMID: 38558979 PMCID: PMC10979840 DOI: 10.1101/2024.03.08.584131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Progressive Rod-Cone Degeneration (PRCD) is an integral membrane protein found in photoreceptor outer segment (OS) disc membranes and its function remains unknown. Mutations in Prcd are implicated in Retinitis pigmentosa (RP) in humans and multiple dog breeds. PRCD-deficient models exhibit decreased levels of cholesterol in the plasma. However, potential changes in the retinal cholesterol remain unexplored. In addition, impaired phagocytosis observed in these animal models points to potential deficits in the retinal pigment epithelium (RPE). Here, using a Prcd -/- murine model we investigated the alterations in the retinal cholesterol levels and impairments in the structural and functional integrity of the RPE. Lipidomic and immunohistochemical analyses show a 5-fold increase in the levels of cholesteryl esters (C.Es) and accumulation of neutral lipids in the PRCD-deficient retina, respectively, indicating alterations in total retinal cholesterol. Longitudinal fundus and spectral domain optical coherence tomography (SD-OCT) examinations showed focal lesions and RPE hyperreflectivity. Strikingly, the RPE of Prcd -/- mice exhibited age-related pathological features such as neutral lipid deposits, lipofuscin accumulation, Bruch's membrane (BrM) thickening and drusenoid focal deposits, mirroring an Age-related Macular Degeneration (AMD)-like phenotype. We propose that the extensive lipofuscin accumulation likely impairs lysosomal function, leading to the defective phagocytosis observed in Prcd -/- mice. Our findings support the dysregulation of retinal cholesterol homeostasis in the absence of PRCD. Further, we demonstrate that progressive photoreceptor degeneration in Prcd -/- mice is accompanied by progressive structural and functional deficits in the RPE, which likely exacerbates vision loss over time.
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3
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Grubaugh CR, Dhingra A, Prakash B, Montenegro D, Sparrow JR, Daniele LL, Curcio CA, Bell BA, Hussain MM, Boesze-Battaglia K. Microsomal triglyceride transfer protein is necessary to maintain lipid homeostasis and retinal function. FASEB J 2024; 38:e23522. [PMID: 38445789 PMCID: PMC10949407 DOI: 10.1096/fj.202302491r] [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: 12/02/2023] [Revised: 02/07/2024] [Accepted: 02/16/2024] [Indexed: 03/07/2024]
Abstract
Lipid processing by the retinal pigment epithelium (RPE) is necessary to maintain retinal health and function. Dysregulation of retinal lipid homeostasis due to normal aging or age-related disease triggers lipid accumulation within the RPE, on Bruch's membrane (BrM), and in the subretinal space. In its role as a hub for lipid trafficking into and out of the neural retina, the RPE packages a significant amount of lipid into lipid droplets for storage and into apolipoprotein B (APOB)-containing lipoproteins (Blps) for export. Microsomal triglyceride transfer protein (MTP), encoded by the MTTP gene, is essential for Blp assembly. Herein we test the hypothesis that MTP expression in the RPE is essential to maintain lipid balance and retinal function using the newly generated RPEΔMttp mouse model. Using non-invasive ocular imaging, electroretinography, and histochemical and biochemical analyses we show that genetic depletion of Mttp from the RPE results in intracellular lipid accumulation, increased photoreceptor-associated cholesterol deposits, and photoreceptor cell death, and loss of rod but not cone function. RPE-specific reduction in Mttp had no significant effect on plasma lipids and lipoproteins. While APOB was decreased in the RPE, most ocular retinoids remained unchanged, with the exception of the storage form of retinoid, retinyl ester. Thus suggesting that RPE MTP is critical for Blp synthesis and assembly but is not directly involved in plasma lipoprotein metabolism. These studies demonstrate that RPE-specific MTP expression is necessary to establish and maintain retinal lipid homeostasis and visual function.
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Affiliation(s)
- Catharina R. Grubaugh
- Department of Basic and Translational Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Anuradha Dhingra
- Department of Basic and Translational Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Binu Prakash
- Department of Foundations of Medicine, New York University Grossman Long Island School of Medicine, Mineola, NY, 11501 USA
| | - Diego Montenegro
- Department of Ophthalmology and Department of Pathology and Cell Biology, Columbia University, New York, NY, 10027 USA
| | - Janet R. Sparrow
- Department of Ophthalmology and Department of Pathology and Cell Biology, Columbia University, New York, NY, 10027 USA
| | - Lauren L. Daniele
- Department of Basic and Translational Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Christine A. Curcio
- Department of Ophthalmology and Visual Sciences, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Brent A. Bell
- Department of Ophthalmology, University of Pennsylvania, Philadelphia, PA, 19104 USA
| | - M. Mahmood Hussain
- Department of Foundations of Medicine, New York University Grossman Long Island School of Medicine, Mineola, NY, 11501 USA
| | - Kathleen Boesze-Battaglia
- Department of Basic and Translational Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
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4
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Grubaugh CR, Dhingra A, Prakash B, Montenegro D, Sparrow JR, Daniele LL, Curcio CA, Bell BA, Hussain MM, Boesze-Battaglia K. Microsomal triglyceride transfer protein is necessary to maintain lipid homeostasis and retinal function. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.06.570418. [PMID: 38105975 PMCID: PMC10723417 DOI: 10.1101/2023.12.06.570418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
Lipid processing by the retinal pigment epithelium (RPE) is necessary to maintain retinal health and function. Dysregulation of retinal lipid homeostasis due to normal aging or to age-related disease triggers lipid accumulation within the RPE, on Bruch's membrane (BrM), and in the subretinal space. In its role as a hub for lipid trafficking into and out of the neural retina, the RPE packages a significant amount of lipid into lipid droplets for storage and into apolipoprotein B (apoB)-containing lipoproteins (Blps) for export. Microsomal triglyceride transfer protein (MTP), encoded by the MTTP gene, is essential for Blp assembly. Herein we test the hypothesis that MTP expression in the RPE is essential to maintain lipid balance and retinal function using the newly generated RPEΔMttp mouse model. Using non-invasive ocular imaging, electroretinography, and histochemical and biochemical analyses we show that genetic deletion of Mttp from the RPE results in intracellular lipid accumulation, increased photoreceptor -associated cholesterol deposits and photoreceptor cell death, and loss of rod but not cone function. RPE-specific ablation of Mttp had no significant effect on plasma lipids and lipoproteins. While, apoB was decreased in the RPE, ocular retinoid concentrations remained unchanged. Thus suggesting that RPE MTP is critical for Blp synthesis and assembly but not directly involved in ocular retinoid and plasma lipoprotein metabolism. These studies demonstrate that RPE-specific MTP expression is necessary to establish and maintain retinal lipid homeostasis and visual function.
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Affiliation(s)
- Catharina R. Grubaugh
- Department of Basic and Translational Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Anuradha Dhingra
- Department of Basic and Translational Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Binu Prakash
- Department of Foundations of Medicine, New York University Grossman Long Island School of Medicine, Mineola, NY, 11501 USA
| | - Diego Montenegro
- Department of Ophthalmology and Department of Pathology and Cell Biology, Columbia University, New York, NY,10027 USA
| | - Janet R. Sparrow
- Department of Ophthalmology and Department of Pathology and Cell Biology, Columbia University, New York, NY,10027 USA
| | - Lauren L. Daniele
- Department of Basic and Translational Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Christine A. Curcio
- Department of Ophthalmology and Visual Sciences, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Brent A. Bell
- Department of Ophthalmology, University of Pennsylvania, Philadelphia, PA, 19104 USA
| | - M. Mahmood Hussain
- Department of Foundations of Medicine, New York University Grossman Long Island School of Medicine, Mineola, NY, 11501 USA
| | - Kathleen Boesze-Battaglia
- Department of Basic and Translational Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
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Kuroha S, Katada Y, Isobe Y, Uchino H, Shishikura K, Nirasawa T, Tsubota K, Negishi K, Kurihara T, Arita M. Long chain acyl-CoA synthetase 6 facilitates the local distribution of di-docosahexaenoic acid- and ultra-long-chain-PUFA-containing phospholipids in the retina to support normal visual function in mice. FASEB J 2023; 37:e23151. [PMID: 37585289 DOI: 10.1096/fj.202300976r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2023] [Revised: 07/31/2023] [Accepted: 08/04/2023] [Indexed: 08/18/2023]
Abstract
Docosahexaenoic acid (DHA) and ultra-long-chain polyunsaturated fatty acids (ULC-PUFAs) are uniquely enriched in membrane phospholipids of retinal photoreceptors. Several studies have shown that di-DHA- and ULC-PUFA-containing phospholipids in photoreceptors have an important role in maintaining normal visual function; however, the molecular mechanisms underlying the synthesis and enrichment of these unique lipids in the retina, and their specific roles in retinal function remain unclear. Long-chain acyl-coenzyme A (CoA) synthetase 6 (ACSL6) preferentially converts DHA into DHA-CoA, which is a substrate during DHA-containing lipid biosynthesis. Here, we report that Acsl6 mRNA is expressed in the inner segment of photoreceptor cells and the retinal pigment epithelial cells, and genetic deletion of ACSL6 resulted in the selective depletion of di-DHA- and ULC-PUFA-containing phospholipids, but not mono-DHA-containing phospholipids in the retina. MALDI mass spectrometry imaging (MALDI-MSI) revealed the selective distribution of di-DHA- and ULC-PUFA-containing phospholipids in the photoreceptor outer segment (OS). Electroretinogram of Acsl6-/- mice exhibited photoreceptor cell-derived visual impairment, whereas the expression levels and localization of opsin proteins were unchanged. Acsl6-/- mice exhibited an age-dependent progressive decrease of the thickness of the outer nuclear layers, whereas the inner nuclear layers and OSs were normal. These results demonstrate that ACSL6 facilitates the local enrichment of di-DHA- and ULC-PUFA-containing phospholipids in the retina, which supports normal visual function and retinal homeostasis.
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Affiliation(s)
- Sayoko Kuroha
- Division of Physiological Chemistry and Metabolism, Graduate School of Pharmaceutical Sciences, Keio University, Tokyo, Japan
- Laboratory for Metabolomics, RIKEN Center for Integrative Medical Sciences (IMS), Yokohama, Japan
- Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
- Laboratory of Photobiology, Keio University School of Medicine, Tokyo, Japan
| | - Yusaku Katada
- Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
- Laboratory of Photobiology, Keio University School of Medicine, Tokyo, Japan
| | - Yosuke Isobe
- Division of Physiological Chemistry and Metabolism, Graduate School of Pharmaceutical Sciences, Keio University, Tokyo, Japan
- Laboratory for Metabolomics, RIKEN Center for Integrative Medical Sciences (IMS), Yokohama, Japan
| | - Haruki Uchino
- Division of Physiological Chemistry and Metabolism, Graduate School of Pharmaceutical Sciences, Keio University, Tokyo, Japan
- Laboratory for Metabolomics, RIKEN Center for Integrative Medical Sciences (IMS), Yokohama, Japan
| | - Kyosuke Shishikura
- Laboratory for Metabolomics, RIKEN Center for Integrative Medical Sciences (IMS), Yokohama, Japan
- Cellular and Molecular Epigenetics Laboratory, Graduate School of Medical Life Science, Yokohama City University, Yokohama, Japan
| | | | | | - Kazuno Negishi
- Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
| | - Toshihide Kurihara
- Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
- Laboratory of Photobiology, Keio University School of Medicine, Tokyo, Japan
| | - Makoto Arita
- Division of Physiological Chemistry and Metabolism, Graduate School of Pharmaceutical Sciences, Keio University, Tokyo, Japan
- Laboratory for Metabolomics, RIKEN Center for Integrative Medical Sciences (IMS), Yokohama, Japan
- Cellular and Molecular Epigenetics Laboratory, Graduate School of Medical Life Science, Yokohama City University, Yokohama, Japan
- Human Biology-Microbiome-Quantum Research Center (WPI-Bio2Q), Keio University, Tokyo, Japan
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6
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Swinkels D, Baes M. The essential role of docosahexaenoic acid and its derivatives for retinal integrity. Pharmacol Ther 2023; 247:108440. [PMID: 37201739 DOI: 10.1016/j.pharmthera.2023.108440] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Revised: 05/08/2023] [Accepted: 05/15/2023] [Indexed: 05/20/2023]
Abstract
The fatty acid composition of photoreceptor outer segment (POS) phospholipids diverges from other membranes, being highly enriched in polyunsaturated fatty acids (PUFAs). The most abundant PUFA is docosahexaenoic acid (DHA, C22:6n-3), an omega-3 PUFA that amounts to over 50% of the POS phospholipid fatty acid side chains. Interestingly, DHA is the precursor of other bioactive lipids such as elongated PUFAs and oxygenated derivatives. In this review, we present the current view on metabolism, trafficking and function of DHA and very long chain polyunsaturated fatty acids (VLC-PUFAs) in the retina. New insights on pathological features generated from PUFA deficient mouse models with enzyme or transporter defects and corresponding patients are discussed. Not only the neural retina, but also abnormalities in the retinal pigment epithelium are considered. Furthermore, the potential involvement of PUFAs in more common retinal degeneration diseases such as diabetic retinopathy, retinitis pigmentosa and age-related macular degeneration are evaluated. Supplementation treatment strategies and their outcome are summarized.
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Affiliation(s)
- Daniëlle Swinkels
- Laboratory of Cell Metabolism, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, 3000 Leuven, Belgium
| | - Myriam Baes
- Laboratory of Cell Metabolism, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, 3000 Leuven, Belgium.
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Rizzo G, Baroni L, Lombardo M. Promising Sources of Plant-Derived Polyunsaturated Fatty Acids: A Narrative Review. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2023; 20:1683. [PMID: 36767052 PMCID: PMC9914036 DOI: 10.3390/ijerph20031683] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2022] [Revised: 01/11/2023] [Accepted: 01/15/2023] [Indexed: 06/01/2023]
Abstract
(1) Background: Polyunsaturated fatty acids (PUFAs) are known for their ability to protect against numerous metabolic disorders. The consumption of oily fish is the main source of PUFAs in human nutrition and is commonly used for supplement production. However, seafood is an overexploited source that cannot be guaranteed to cover the global demands. Furthermore, it is not consumed by everyone for ecological, economic, ethical, geographical and taste reasons. The growing demand for natural dietary sources of PUFAs suggests that current nutritional sources are insufficient to meet global needs, and less and less will be. Therefore, it is crucial to find sustainable sources that are acceptable to all, meeting the world population's needs. (2) Scope: This review aims to evaluate the recent evidence about alternative plant sources of essential fatty acids, focusing on long-chain omega-3 (n-3) PUFAs. (3) Method: A structured search was performed on the PubMed search engine to select available human data from interventional studies using omega-3 fatty acids of non-animal origin. (4) Results: Several promising sources have emerged from the literature, such as algae, microorganisms, plants rich in stearidonic acid and GM plants. However, the costs, acceptance and adequate formulation deserve further investigation.
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Affiliation(s)
- Gianluca Rizzo
- Independent Researcher, Via Venezuela 66, 98121 Messina, Italy
| | - Luciana Baroni
- Scientific Society for Vegetarian Nutrition, 30171 Venice, Italy
| | - Mauro Lombardo
- Department of Human Sciences and Promotion of the Quality of Life, San Raffaele Open University, 00166 Rome, Italy
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Rosenhouse-Dantsker A, Gazgalis D, Logothetis DE. PI(4,5)P 2 and Cholesterol: Synthesis, Regulation, and Functions. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1422:3-59. [PMID: 36988876 DOI: 10.1007/978-3-031-21547-6_1] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 03/30/2023]
Abstract
Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) is the most abundant membrane phosphoinositide and cholesterol is an essential component of the plasma membrane (PM). Both lipids play key roles in a variety of cellular functions including as signaling molecules and major regulators of protein function. This chapter provides an overview of these two important lipids. Starting from a brief description of their structure, synthesis, and regulation, the chapter continues to describe the primary functions and signaling processes in which PI(4,5)P2 and cholesterol are involved. While PI(4,5)P2 and cholesterol can act independently, they often act in concert or affect each other's impact. The chapters in this volume on "Cholesterol and PI(4,5)P2 in Vital Biological Functions: From Coexistence to Crosstalk" focus on the emerging relationship between cholesterol and PI(4,5)P2 in a variety of biological systems and processes. In this chapter, the next section provides examples from the ion channel field demonstrating that PI(4,5)P2 and cholesterol can act via common mechanisms. The chapter ends with a discussion of future directions.
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Affiliation(s)
| | - Dimitris Gazgalis
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, MA, USA
| | - Diomedes E Logothetis
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, MA, USA
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Verra DM, Spinnhirny P, Sandu C, Grégoire S, Acar N, Berdeaux O, Brétillon L, Sparrow JR, Hicks D. Intrinsic differences in rod and cone membrane composition: implications for cone degeneration. Graefes Arch Clin Exp Ophthalmol 2022; 260:3131-3148. [PMID: 35524799 DOI: 10.1007/s00417-022-05684-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 04/19/2022] [Accepted: 04/22/2022] [Indexed: 11/04/2022] Open
Abstract
PURPOSE In many retinal pathological conditions, rod and cone degeneration differs. For example, the early-onset maculopathy Stargardts disease type 1 (STGD1) is typified by loss of cones while rods are often less affected. We wanted to examine whether there exist intrinsic membrane differences between rods and cones that might explain such features. METHODS Abca4 mRNA and protein levels were quantified in rod- and cone-enriched samples from wild-type and Nrl-/- mice retinas; rod- and cone-enriched outer segments (ROS and COS respectively) were prepared from pig retinas, and total lipids were analyzed by flame ionization, chromatography, and tandem mass spectrometry. Immunohistochemical staining of cone-rich rodent Arvicanthis ansorgei retinas was conducted, and ultra-high performance liquid chromatography of lipid species in porcine ROS and COS was performed. RESULTS Abca4 mRNA and Abca4 protein content was significantly higher (50-300%) in cone compared to rod-enriched samples. ROS and COS displayed dramatic differences in several lipids, including very long chain poly-unsaturated fatty acids (VLC-PUFAs), especially docosahexaenoic acid (DHA, 22:6n-3): ROS 20.6% DHA, COS 3.3% (p < 0.001). VLC-PUFAs (> 50 total carbons) were virtually absent from COS. COS were impoverished (> 6× less) in phosphatidylethanolamine compared to ROS. ELOVL4 ("ELOngation of Very Long chain fatty acids 4") antibody labelled Arvicanthis cones only very weakly compared to rods. Finally, there were large amounts (905 a.u.) of the bisretinoid A2PE in ROS, whereas it was much lower (121 a.u., ~ 7.5-fold less) in COS fractions. In contrast, COS contained fivefold higher amounts of all-trans-retinal dimer (115 a.u. compared to 22 a.u. in rods). CONCLUSIONS Compared to rods, cones expressed higher levels of Abca4 mRNA and Abca4 protein, were highly impoverished in PUFA (especially DHA) and phosphatidylethanolamine, and contained significant amounts of all-trans-retinal dimer. Based on these and other data, we propose that in contrast to rods, cones are preferentially vulnerable to stress and may die through direct cellular toxicity in pathologies such as STGD1.
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Affiliation(s)
- Daniela M Verra
- Département de Neurobiologie des Rythmes, Institut des Neurosciences Cellulaires et Intégratives, CNRS UPR 3212, 8 Allée Général Rouvillois, 67000, Strasbourg Cedex, France
| | - Perrine Spinnhirny
- Département de Neurobiologie des Rythmes, Institut des Neurosciences Cellulaires et Intégratives, CNRS UPR 3212, 8 Allée Général Rouvillois, 67000, Strasbourg Cedex, France
| | - Cristina Sandu
- Département de Neurobiologie des Rythmes, Institut des Neurosciences Cellulaires et Intégratives, CNRS UPR 3212, 8 Allée Général Rouvillois, 67000, Strasbourg Cedex, France
| | - Stéphane Grégoire
- UMR 1324 Centre des Sciences du Goût et de l'Alimentation, Eye and Nutrition Research Group, INRA, Dijon, France.,UMR 6265 Centre des Sciences du Goût et de l'Alimentation, CNRS, Dijon, France.,Centre des Sciences du Goût et de l'Alimentation, Université de Bourgogne, Dijon, France
| | - Niyazi Acar
- UMR 1324 Centre des Sciences du Goût et de l'Alimentation, Eye and Nutrition Research Group, INRA, Dijon, France.,UMR 6265 Centre des Sciences du Goût et de l'Alimentation, CNRS, Dijon, France.,Centre des Sciences du Goût et de l'Alimentation, Université de Bourgogne, Dijon, France
| | - Olivier Berdeaux
- UMR 1324 Centre des Sciences du Goût et de l'Alimentation, Eye and Nutrition Research Group, INRA, Dijon, France.,UMR 6265 Centre des Sciences du Goût et de l'Alimentation, CNRS, Dijon, France.,Centre des Sciences du Goût et de l'Alimentation, Université de Bourgogne, Dijon, France
| | - Lionel Brétillon
- UMR 1324 Centre des Sciences du Goût et de l'Alimentation, Eye and Nutrition Research Group, INRA, Dijon, France.,UMR 6265 Centre des Sciences du Goût et de l'Alimentation, CNRS, Dijon, France.,Centre des Sciences du Goût et de l'Alimentation, Université de Bourgogne, Dijon, France
| | - Janet R Sparrow
- Departments of Ophthalmology, and Pathology and Cell Biology, Columbia University Medical Center, New York, NY, USA
| | - David Hicks
- Département de Neurobiologie des Rythmes, Institut des Neurosciences Cellulaires et Intégratives, CNRS UPR 3212, 8 Allée Général Rouvillois, 67000, Strasbourg Cedex, France.
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10
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Lewandowski D, Sander CL, Tworak A, Gao F, Xu Q, Skowronska-Krawczyk D. Dynamic lipid turnover in photoreceptors and retinal pigment epithelium throughout life. Prog Retin Eye Res 2021; 89:101037. [PMID: 34971765 PMCID: PMC10361839 DOI: 10.1016/j.preteyeres.2021.101037] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 12/13/2021] [Accepted: 12/15/2021] [Indexed: 12/13/2022]
Abstract
The retinal pigment epithelium-photoreceptor interphase is renewed each day in a stunning display of cellular interdependence. While photoreceptors use photosensitive pigments to convert light into electrical signals, the RPE supports photoreceptors in their function by phagocytizing shed photoreceptor tips, regulating the blood retina barrier, and modulating inflammatory responses, as well as regenerating the 11-cis-retinal chromophore via the classical visual cycle. These processes involve multiple protein complexes, tightly regulated ligand-receptors interactions, and a plethora of lipids and protein-lipids interactions. The role of lipids in maintaining a healthy interplay between the RPE and photoreceptors has not been fully delineated. In recent years, novel technologies have resulted in major advancements in understanding several facets of this interplay, including the involvement of lipids in phagocytosis and phagolysosome function, nutrient recycling, and the metabolic dependence between the two cell types. In this review, we aim to integrate the complex role of lipids in photoreceptor and RPE function, emphasizing the dynamic exchange between the cells as well as discuss how these processes are affected in aging and retinal diseases.
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Affiliation(s)
- Dominik Lewandowski
- Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA
| | - Christopher L Sander
- Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA; Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Aleksander Tworak
- Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA
| | - Fangyuan Gao
- Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA
| | - Qianlan Xu
- Department of Physiology and Biophysics, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA; Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA
| | - Dorota Skowronska-Krawczyk
- Department of Physiology and Biophysics, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA; Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA.
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11
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West AL, Miles EA, Han L, Lillycrop KA, Napier JA, Calder PC, Burdge GC. Dietary Supplementation with Transgenic Camelina sativa Oil Containing 20:5n-3 and 22:6n-3 or Fish Oil Induces Differential Changes in the Transcriptome of CD3 + T Lymphocytes. Nutrients 2021; 13:3116. [PMID: 34578993 PMCID: PMC8466821 DOI: 10.3390/nu13093116] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 08/31/2021] [Accepted: 09/02/2021] [Indexed: 12/23/2022] Open
Abstract
Eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3) are important for leukocyte function. This study investigated whether consuming transgenic Camelina sativa (tCSO) seed oil containing both 20:5n-3 and 22:6n-3 is as effective as fish oil (FO) for increasing the 20:5n-3 and 22:6n-3 content of leukocytes and altering mitogen-induced changes to the T cell transcriptome. Healthy adults (n = 31) consumed 450 mg/day of 20:5n-3 plus 22:6n-3 from either FO or tCSO for 8 weeks. Blood was collected before and after the intervention. 20:5n-3 and 22:6n-3 incorporation from tCSO into immune cell total lipids was comparable to FO. The relative expression of the transcriptomes of mitogen-stimulated versus unstimulated T lymphocytes in a subgroup of 16 women/test oil showed 4390 transcripts were differentially expressed at Baseline (59% up-regulated), 4769 (57% up-regulated) after FO and 3443 (38% up-regulated) after tCSO supplementation. The 20 most altered transcripts after supplementation differed between test oils. The most altered pathways were associated with cell proliferation and immune function. In conclusion, 20:5n-3 and 22:6n-3 incorporation into immune cells from tCSO was comparable to FO and can modify mitogen-induced changes in the T cell transcriptome, contingent on the lipid matrix of the oil.
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Affiliation(s)
- Annette L. West
- School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton SO16 6YD, UK; (A.L.W.); (E.A.M.); (P.C.C.)
| | - Elizabeth A. Miles
- School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton SO16 6YD, UK; (A.L.W.); (E.A.M.); (P.C.C.)
| | - Lihua Han
- Department of Plant Sciences, Rothamsted Research, Harpenden AL5 2JQ, UK; (L.H.); (J.A.N.)
| | - Karen A. Lillycrop
- Centre for Biological Sciences, Faculty of Environmental and Life Sciences, University of Southampton, Southampton SO17 1BJ, UK;
| | - Johnathan A. Napier
- Department of Plant Sciences, Rothamsted Research, Harpenden AL5 2JQ, UK; (L.H.); (J.A.N.)
| | - Philip C. Calder
- School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton SO16 6YD, UK; (A.L.W.); (E.A.M.); (P.C.C.)
- NIHR Southampton Biomedical Research Centre, University Hospital Southampton NHS Foundation Trust and University of Southampton, Southampton SO16 6YD, UK
| | - Graham C. Burdge
- School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton SO16 6YD, UK; (A.L.W.); (E.A.M.); (P.C.C.)
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12
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Fasting increases 18:2-containing phosphatidylcholines to complement the decrease in 22:6-containing phosphatidylcholines in mouse skeletal muscle. PLoS One 2021; 16:e0255178. [PMID: 34310656 PMCID: PMC8312970 DOI: 10.1371/journal.pone.0255178] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 07/10/2021] [Indexed: 12/15/2022] Open
Abstract
Fasting stimulates catabolic reactions in skeletal muscle to survive nutrient deprivation. Cellular phospholipids have large structural diversity due to various polar-heads and acyl-chains that affect many cellular functions. Skeletal muscle phospholipid profiles have been suggested to be associated with muscle adaptations to nutritional and environmental status. However, the effect of fasting on skeletal muscle phospholipid profiles remains unknown. Here, we analyzed phospholipids using liquid chromatography mass spectrometry. We determined that fasting resulted in a decrease in 22:6-containing phosphatidylcholines (PCs) (22:6-PCs) and an increase in 18:2-containing PCs (18:2-PCs). The fasting-induced increase in 18:2-PCs was sufficient to complement 22:6-PCs loss, resulting in the maintenance of the total amount of polyunsaturated fatty acid (PUFA)-containing PCs. Similar phospholipid alterations occurred in insulin-deficient mice, which indicate that these observed phospholipid perturbations were characteristic of catabolic skeletal muscle. In lysophosphatidic acid acyltransferase 3-knockout muscles that mostly lack 22:6-PCs, other PUFA-containing PCs, mainly 18:2-PCs, accumulated. This suggests a compensatory mechanism for skeletal muscles to maintain PUFA-containing PCs.
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13
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Vidal E, Jun B, Gordon WC, Maire MA, Martine L, Grégoire S, Khoury S, Cabaret S, Berdeaux O, Acar N, Bretillon L, Bazan NG. Bioavailability and spatial distribution of fatty acids in the rat retina after dietary omega-3 supplementation. J Lipid Res 2020; 61:1733-1746. [PMID: 33127836 PMCID: PMC7707163 DOI: 10.1194/jlr.ra120001057] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Spatial changes of FAs in the retina in response to different dietary n-3 formulations have never been explored, although a diet rich in EPA and DHA is recommended to protect the retina against the effects of aging. In this study, Wistar rats were fed for 8 weeks with balanced diet including either EPA-containing phospholipids (PLs), EPA-containing TGs, DHA-containing PLs, or DHA-containing TGs. Qualitative changes in FA composition of plasma, erythrocytes, and retina were evaluated by gas chromatography-flame ionization detector. Following the different dietary intakes, changes to the quantity and spatial organization of PC and PE species in retina were determined by LC coupled to MS/MS and MALDI coupled to MS imaging. The omega-3 content in the lipids of plasma and erythrocytes suggests that PLs as well as TGs are good omega-3 carriers for retina. However, a significant increase in DHA content in retina was observed, especially molecular species as di-DHA-containing PC and PE, as well as an increase in very long chain PUFAs (more than 28 carbons) following PL-EPA and TG-DHA diets only. All supplemented diets triggered spatial organization changes of DHA in the photoreceptor layer around the optic nerve. Taken together, these findings suggest that dietary omega-3 supplementation can modify the content of FAs in the rat retina.
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Affiliation(s)
- Elisa Vidal
- Eye and Nutrition Research Group, Centre des Sciences du Goût et de l'Alimentation, AgroSup Dijon, INRAE, CNRS, Université Bourgogne Franche-Comté, Dijon, France; Horus Pharma Laboratories, Saint Laurent du Var, France
| | - Bokkyoo Jun
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, LA, USA
| | - William C Gordon
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, LA, USA
| | - Marie-Annick Maire
- Eye and Nutrition Research Group, Centre des Sciences du Goût et de l'Alimentation, AgroSup Dijon, INRAE, CNRS, Université Bourgogne Franche-Comté, Dijon, France
| | - Lucy Martine
- Eye and Nutrition Research Group, Centre des Sciences du Goût et de l'Alimentation, AgroSup Dijon, INRAE, CNRS, Université Bourgogne Franche-Comté, Dijon, France
| | - Stéphane Grégoire
- Eye and Nutrition Research Group, Centre des Sciences du Goût et de l'Alimentation, AgroSup Dijon, INRAE, CNRS, Université Bourgogne Franche-Comté, Dijon, France
| | - Spiro Khoury
- Chemosens Group, Centre des Sciences du Goût et de l'Alimentation, AgroSup Dijon, CNRS, INRAE, Université Bourgogne Franche-Comté, Dijon, France
| | - Stephanie Cabaret
- Chemosens Group, Centre des Sciences du Goût et de l'Alimentation, AgroSup Dijon, CNRS, INRAE, Université Bourgogne Franche-Comté, Dijon, France
| | - Olivier Berdeaux
- Chemosens Group, Centre des Sciences du Goût et de l'Alimentation, AgroSup Dijon, CNRS, INRAE, Université Bourgogne Franche-Comté, Dijon, France
| | - Niyazi Acar
- Eye and Nutrition Research Group, Centre des Sciences du Goût et de l'Alimentation, AgroSup Dijon, INRAE, CNRS, Université Bourgogne Franche-Comté, Dijon, France
| | - Lionel Bretillon
- Eye and Nutrition Research Group, Centre des Sciences du Goût et de l'Alimentation, AgroSup Dijon, INRAE, CNRS, Université Bourgogne Franche-Comté, Dijon, France.
| | - Nicolas G Bazan
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, LA, USA
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Nechipurenko IV. The Enigmatic Role of Lipids in Cilia Signaling. Front Cell Dev Biol 2020; 8:777. [PMID: 32850869 PMCID: PMC7431879 DOI: 10.3389/fcell.2020.00777] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Accepted: 07/24/2020] [Indexed: 12/21/2022] Open
Abstract
Primary cilia are specialized cellular structures that project from the surface of most cell types in metazoans and mediate transduction of major signaling pathways. The ciliary membrane is contiguous with the plasma membrane, yet it exhibits distinct protein and lipid composition, which is essential for ciliary function. Diffusion barriers at the base of a cilium are responsible for establishing unique molecular composition of this organelle. Although considerable progress has been made in identifying mechanisms of ciliary protein trafficking in and out of cilia, it remains largely unknown how the distinct lipid identity of the ciliary membrane is achieved. In this mini review, I summarize recent developments in characterizing lipid composition and organization of the ciliary membrane and discuss the emerging roles of lipids in modulating activity of ciliary signaling components including ion channels and G protein-coupled receptors.
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Affiliation(s)
- Inna V. Nechipurenko
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, MA, United States
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15
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Duncan AL, Song W, Sansom MSP. Lipid-Dependent Regulation of Ion Channels and G Protein-Coupled Receptors: Insights from Structures and Simulations. Annu Rev Pharmacol Toxicol 2019; 60:31-50. [PMID: 31506010 DOI: 10.1146/annurev-pharmtox-010919-023411] [Citation(s) in RCA: 96] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Ion channels and G protein-coupled receptors (GPCRs) are regulated by lipids in their membrane environment. Structural studies combined with biophysical and molecular simulation investigations reveal interaction sites for specific lipids on membrane protein structures. For K channels, PIP2 plays a key role in regulating Kv and Kir channels. Likewise, several recent cryo-EM structures of TRP channels have revealed bound lipids, including PIP2 and cholesterol. Among the pentameric ligand-gated ion channel family, structural and biophysical studies suggest the M4 TM helix may act as a lipid sensor, e.g., forming part of the binding sites for neurosteroids on the GABAA receptor. Structures of GPCRs have revealed multiple cholesterol sites, which may modulate both receptor dynamics and receptor oligomerization. PIP2 also interacts with GPCRs and may modulate their interactions with G proteins. Overall, it is evident that multiple lipid binding sites exist on channels and receptors that modulate their function allosterically and are potential druggable sites.
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Affiliation(s)
- Anna L Duncan
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom;
| | - Wanling Song
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom;
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom;
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16
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Park PSH. Rhodopsin Oligomerization and Aggregation. J Membr Biol 2019; 252:413-423. [PMID: 31286171 DOI: 10.1007/s00232-019-00078-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Accepted: 06/25/2019] [Indexed: 12/18/2022]
Abstract
Rhodopsin is the light receptor in photoreceptor cells of the retina and a prototypical G protein-coupled receptor. Two types of quaternary structures can be adopted by rhodopsin. If rhodopsin folds and attains a proper tertiary structure, it can then form oligomers and nanodomains within the photoreceptor cell membrane. In contrast, if rhodopsin misfolds, it cannot progress through the biosynthetic pathway and instead will form aggregates that can cause retinal degenerative disease. In this review, emerging views are highlighted on the supramolecular organization of rhodopsin within the membrane of photoreceptor cells and the aggregation of rhodopsin that can lead to retinal degeneration.
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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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17
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Shaw LC, Li Calzi S, Li N, Moldovan L, Sengupta-Caballero N, Quigley JL, Ivan M, Jun B, Bazan NG, Boulton ME, Busik J, Neu J, Grant MB. Enteral Arg-Gln Dipeptide Administration Increases Retinal Docosahexaenoic Acid and Neuroprotectin D1 in a Murine Model of Retinopathy of Prematurity. Invest Ophthalmol Vis Sci 2018; 59:858-869. [PMID: 29490339 PMCID: PMC5815421 DOI: 10.1167/iovs.17-23034] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose Low levels of the long chain polyunsaturated fatty acid (LCPUFA) docosahexaenoic acid (DHA) have been implicated in retinopathy of prematurity (ROP). However, oral DHA suffers from poor palatability and is associated with increased bleeding in premature infants. We asked whether oral administration of the neutraceutical arginine-glutamine (Arg-Glu) could increase retinal DHA and improve outcomes in a mouse model of oxygen-induced retinopathy (OIR). Methods Postnatal day 7 (P7) pups were maintained at 75% oxygen for 5 days and then returned to room air on P12. Pups were gavaged twice daily with Arg-Gln or vehicle from P12 to P17 and eyes were harvested for analysis on P17. Vaso-obliteration and vascular density were assessed on retinal flat mounts and preretinal neovascularization was assessed on retinal cross sections. Retinas were used for measurement of DHA and 10,17S-docosatriene (neuroprotectin D1, NPD1), a key DHA-derived lipid, and for analysis by reverse-phase protein array (RPPA). Results With Arg-Gln treatment, retinal DHA and NPD1 levels were increased in OIR pups. Arg-Gln reduced preretinal neovascularization by 39 ± 6% (P < 0.05) relative to vehicle control. This was accompanied by a restoration of vascular density of the retina in the pups treated with Arg-Gln (73.0 ± 3.0%) compared to vehicle (53.1 ± 3.4%; P < 0.05). Arg-Gln dipeptide restored OIR-induced signaling changes toward normoxia and was associated with normalization of insulin-like growth factor receptor 1 signaling and reduction of apoptosis and an increase in anti-apoptosis proteins. Conclusions Arg-Gln may serve as a safer and easily tolerated nutraceutical agent for prevention or treatment of ROP.
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Affiliation(s)
- Lynn Calvin Shaw
- Department of Ophthalmology, Indiana University, Indianapolis, Indiana, United States
| | - Sergio Li Calzi
- Department of Ophthalmology, University of Alabama, Birmingham, Alabama, United States
| | - Nan Li
- Department of Pediatrics, University of Florida, Gainesville, Florida, United States
| | - Leni Moldovan
- Department of Ophthalmology, Indiana University, Indianapolis, Indiana, United States
| | | | | | - Mircea Ivan
- Department of Medicine, Indiana University, Indianapolis, Indiana, United States
| | - Bokkyoo Jun
- Department of Ophthalmology, Louisiana State University Eye Center, New Orleans, Louisiana, United States
| | - Nicolas G Bazan
- Department of Ophthalmology, Louisiana State University Eye Center, New Orleans, Louisiana, United States
| | - Michael Edwin Boulton
- Department of Ophthalmology, University of Alabama, Birmingham, Alabama, United States
| | - Julia Busik
- Department of Physiology, Michigan State University, East Lansing, Michigan, United States
| | - Josef Neu
- Department of Pediatrics, University of Florida, Gainesville, Florida, United States
| | - Maria B Grant
- Department of Ophthalmology, University of Alabama, Birmingham, Alabama, United States
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18
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Senapati S, Gragg M, Samuels IS, Parmar VM, Maeda A, Park PSH. Effect of dietary docosahexaenoic acid on rhodopsin content and packing in photoreceptor cell membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:1403-1413. [PMID: 29626443 DOI: 10.1016/j.bbamem.2018.03.030] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 03/13/2018] [Accepted: 03/30/2018] [Indexed: 01/03/2023]
Abstract
Docosahexaenoic acid (DHA) is enriched in photoreceptor cell membranes. DHA deficiency impairs vision due to photoreceptor cell dysfunction, which is caused, at least in part, by reduced activity of rhodopsin, the light receptor that initiates phototransduction. It is unclear how the depletion of membrane DHA impacts the structural properties of rhodopsin and, in turn, its activity. Atomic force microscopy (AFM) was used to assess the impact of DHA deficiency on membrane structure and rhodopsin organization. AFM revealed that signaling impairment in photoreceptor cells is independent of the oligomeric status of rhodopsin and causes adaptations in photoreceptor cells where the content and density of rhodopsin in the membrane is increased. Functional and structural changes caused by DHA deficiency were reversible.
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Affiliation(s)
- Subhadip Senapati
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Megan Gragg
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Ivy S Samuels
- Research Service, Louis Stokes Cleveland Veterans Administration Medical Center, Cleveland, OH 44106, USA; Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH 44195, USA
| | - Vipul M Parmar
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Akiko Maeda
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Paul S-H Park
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA.
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19
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Potvin-Fournier K, Valois-Paillard G, Lefèvre T, Cantin L, Salesse C, Auger M. Membrane fluidity is a driving force for recoverin myristoyl immobilization in zwitterionic lipids. Biochem Biophys Res Commun 2017; 490:1268-1273. [DOI: 10.1016/j.bbrc.2017.07.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 07/02/2017] [Indexed: 01/08/2023]
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20
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Shindou H, Koso H, Sasaki J, Nakanishi H, Sagara H, Nakagawa KM, Takahashi Y, Hishikawa D, Iizuka-Hishikawa Y, Tokumasu F, Noguchi H, Watanabe S, Sasaki T, Shimizu T. Docosahexaenoic acid preserves visual function by maintaining correct disc morphology in retinal photoreceptor cells. J Biol Chem 2017; 292:12054-12064. [PMID: 28578316 PMCID: PMC5519357 DOI: 10.1074/jbc.m117.790568] [Citation(s) in RCA: 102] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2017] [Revised: 06/01/2017] [Indexed: 12/31/2022] Open
Abstract
Docosahexaenoic acid (DHA) has essential roles in photoreceptor cells in the retina and is therefore crucial to healthy vision. Although the influence of dietary DHA on visual acuity is well known and the retina has an abundance of DHA-containing phospholipids (PL-DHA), the mechanisms associated with DHA's effects on visual function are unknown. We previously identified lysophosphatidic acid acyltransferase 3 (LPAAT3) as a PL-DHA biosynthetic enzyme. Here, using comprehensive phospholipid analyses and imaging mass spectroscopy, we found that LPAAT3 is expressed in the inner segment of photoreceptor cells and that PL-DHA disappears from the outer segment in the LPAAT3-knock-out mice. Dynamic light-scattering analysis of liposomes and molecular dynamics simulations revealed that the physical characteristics of DHA reduced membrane-bending rigidity. Following loss of PL-DHA, LPAAT3-knock-out mice exhibited abnormalities in the retinal layers, such as incomplete elongation of the outer segment and decreased thickness of the outer nuclear layers and impaired visual function, as well as disordered disc morphology in photoreceptor cells. Our results indicate that PL-DHA contributes to visual function by maintaining the disc shape in photoreceptor cells and that this is a function of DHA in the retina. This study thus provides the reason why DHA is required for visual acuity and may help inform approaches for overcoming retinal disorders associated with DHA deficiency or dysfunction.
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Affiliation(s)
- Hideo Shindou
- Department of Lipid Signaling, National Center for Global Health and Medicine, Shinjuku-ku, Tokyo 162-8655; Department of Lipid Science, Graduate School of Medicine, University of Tokyo, Bunkyo-ku, Tokyo 113-0033; Agency for Medical Research and Development (AMED)-Core Research for Evolution Science and Technology (CREST), Chiyoda-ku, Tokyo 100-0004.
| | - Hideto Koso
- Division of Molecular and Developmental Biology, Institute of Medical Science, University of Tokyo, Shirokanedai, Minato-ku, Tokyo 108-8639
| | - Junko Sasaki
- Department of Medical Biology, Akita University Graduate School of Medicine, Akita 010-8543
| | - Hiroki Nakanishi
- Research Center for Biosignal, Akita University Graduate School of Medicine, Akita 010-8502; Akita Lipid Technologies, LLC, Akita 010-0825
| | - Hiroshi Sagara
- Medical Proteomics Laboratory, Institute of Medical Science, University of Tokyo, Shirokanedai, Minato-ku, Tokyo 108-8639
| | - Koh M Nakagawa
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Yoshikazu Takahashi
- Department of Lipid Signaling, National Center for Global Health and Medicine, Shinjuku-ku, Tokyo 162-8655
| | - Daisuke Hishikawa
- Department of Lipid Signaling, National Center for Global Health and Medicine, Shinjuku-ku, Tokyo 162-8655
| | - Yoshiko Iizuka-Hishikawa
- Department of Lipid Signaling, National Center for Global Health and Medicine, Shinjuku-ku, Tokyo 162-8655
| | - Fuyuki Tokumasu
- Department of Lipidomics, Graduate School of Medicine, University of Tokyo, Bunkyo-ku, Tokyo 113-0033
| | - Hiroshi Noguchi
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Sumiko Watanabe
- Division of Molecular and Developmental Biology, Institute of Medical Science, University of Tokyo, Shirokanedai, Minato-ku, Tokyo 108-8639
| | - Takehiko Sasaki
- Agency for Medical Research and Development (AMED)-Core Research for Evolution Science and Technology (CREST), Chiyoda-ku, Tokyo 100-0004; Department of Medical Biology, Akita University Graduate School of Medicine, Akita 010-8543; Research Center for Biosignal, Akita University Graduate School of Medicine, Akita 010-8502; Akita Lipid Technologies, LLC, Akita 010-0825
| | - Takao Shimizu
- Department of Lipid Signaling, National Center for Global Health and Medicine, Shinjuku-ku, Tokyo 162-8655; Department of Lipidomics, Graduate School of Medicine, University of Tokyo, Bunkyo-ku, Tokyo 113-0033
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21
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Rong S, Li Y, Guan Y, Zhu L, Zhou Q, Gao M, Pan H, Zou L, Chang D. Long-chain unsaturated fatty acids as possible important metabolites for primary angle-closure glaucoma based on targeted metabolomic analysis. Biomed Chromatogr 2017; 31. [PMID: 28214354 DOI: 10.1002/bmc.3963] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 01/19/2017] [Accepted: 02/15/2017] [Indexed: 11/09/2022]
Affiliation(s)
- Shengzhong Rong
- School of Public Health; Mudanjiang Medical University; Mudanjiang China
| | - Yang Li
- Hongqi Hospital; Mudanjiang Medical University; Mudanjiang China
| | - Yue Guan
- Hongqi Hospital; Mudanjiang Medical University; Mudanjiang China
| | - Lili Zhu
- Department of Foreign Language; Mudanjiang Medical University; Mudanjiang China
| | - Qiang Zhou
- School of Public Health; Harbin Medical University; Harbin China
| | - Mucong Gao
- School of Public Health; Harbin Medical University; Harbin China
| | - Hongzhi Pan
- School of Public Health; Harbin Medical University; Harbin China
| | - Lina Zou
- Hongqi Hospital; Mudanjiang Medical University; Mudanjiang China
| | - Dong Chang
- Department of Clinical Laboratory, Shanghai Pudong Hospital; Fudan University Pudong Medical Center; Shanghai China
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22
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Interaction of G protein coupled receptors and cholesterol. Chem Phys Lipids 2016; 199:61-73. [PMID: 27108066 DOI: 10.1016/j.chemphyslip.2016.04.006] [Citation(s) in RCA: 144] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Revised: 03/30/2016] [Accepted: 04/19/2016] [Indexed: 12/20/2022]
Abstract
G protein coupled receptors (GPCRs) form the largest receptor superfamily in eukaryotic cells. Owing to their seven transmembrane helices, large parts of these proteins are embedded in the cholesterol-rich plasma membrane bilayer. Thus, GPCRs are always in proximity to cholesterol. Some of them are functionally dependent on the specific presence of cholesterol. Over the last years, enormous progress on receptor structures has been achieved. While lipophilic ligands other than cholesterol have been shown to bind either inside the helix bundle or at the receptor-lipid interface, the binding site of cholesterol was either a single transmembrane helix or a groove between two or more transmembrane helices. A clear preference for one of the two membrane leaflets has not been observed. Not surprisingly, many hydrophobic residues (primarily leucine and isoleucine) were found to be involved in cholesterol binding. In most cases, the rough β-face of cholesterol contacted the transmembrane helix bundle rather than the surrounding lipid matrix. The polar hydroxy group of cholesterol was localized near the water-membrane interface with potential hydrogen bonding to residues in receptor loop regions. Although a canonical motif, designated as CCM site, was detected as a specific cholesterol binding site in case of the β2AR, this site was not found to be occupied by cholesterol in other GPCRs possessing the same motif. Cholesterol-receptor interactions can increase the compactness of the receptor structure and are able to enhance the conformational stability towards active or inactive receptor states. Overall, all current data suggest a high plasticity of cholesterol interaction sites in GPCRs.
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23
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Membrane Lipids in Presynaptic Function and Disease. Neuron 2016; 90:11-25. [DOI: 10.1016/j.neuron.2016.02.033] [Citation(s) in RCA: 123] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Revised: 01/28/2016] [Accepted: 02/18/2016] [Indexed: 12/20/2022]
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Akagi S, Kono N, Ariyama H, Shindou H, Shimizu T, Arai H. Lysophosphatidylcholine acyltransferase 1 protects against cytotoxicity induced by polyunsaturated fatty acids. FASEB J 2016; 30:2027-39. [DOI: 10.1096/fj.201500149] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Accepted: 01/27/2016] [Indexed: 12/28/2022]
Affiliation(s)
- Sosuke Akagi
- Department of Health ChemistryGraduate School of Pharmaceutical SciencesThe University of TokyoTokyoJapan
| | - Nozomu Kono
- Department of Health ChemistryGraduate School of Pharmaceutical SciencesThe University of TokyoTokyoJapan
| | - Hiroyuki Ariyama
- Department of Health ChemistryGraduate School of Pharmaceutical SciencesThe University of TokyoTokyoJapan
| | - Hideo Shindou
- Department of Lipid SignalingResearch InstituteNational Center for Global Health and MedicineTokyoJapan
- Japan Agency for Medical Research and Development‐Core Research for Evolutionary Science and Technology (AMED‐CREST)TokyoJapan
| | - Takao Shimizu
- Department of Lipid SignalingResearch InstituteNational Center for Global Health and MedicineTokyoJapan
- Department of LipidomicsGraduate School of MedicineThe University of TokyoTokyoJapan
| | - Hiroyuki Arai
- Department of Health ChemistryGraduate School of Pharmaceutical SciencesThe University of TokyoTokyoJapan
- Japan Agency for Medical Research and Development‐Core Research for Evolutionary Science and Technology (AMED‐CREST)TokyoJapan
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25
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Simón MV, Agnolazza DL, German OL, Garelli A, Politi LE, Agbaga MP, Anderson RE, Rotstein NP. Synthesis of docosahexaenoic acid from eicosapentaenoic acid in retina neurons protects photoreceptors from oxidative stress. J Neurochem 2016; 136:931-46. [PMID: 26662863 DOI: 10.1111/jnc.13487] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Revised: 11/28/2015] [Accepted: 12/02/2015] [Indexed: 12/27/2022]
Abstract
Oxidative stress is involved in activating photoreceptor death in several retinal degenerations. Docosahexaenoic acid (DHA), the major polyunsaturated fatty acid in the retina, protects cultured retina photoreceptors from apoptosis induced by oxidative stress and promotes photoreceptor differentiation. Here, we investigated whether eicosapentaenoic acid (EPA), a metabolic precursor to DHA, had similar effects and whether retinal neurons could metabolize EPA to DHA. Adding EPA to rat retina neuronal cultures increased opsin expression and protected photoreceptors from apoptosis induced by the oxidants paraquat and hydrogen peroxide (H2 O2 ). Palmitic, oleic, and arachidonic acids had no protective effect, showing the specificity for DHA. We found that EPA supplementation significantly increased DHA percentage in retinal neurons, but not EPA percentage. Photoreceptors and glial cells expressed Δ6 desaturase (FADS2), which introduces the last double bond in DHA biosynthetic pathway. Pre-treatment of neuronal cultures with CP-24879 hydrochloride, a Δ5/Δ6 desaturase inhibitor, prevented EPA-induced increase in DHA percentage and completely blocked EPA protection and its effect on photoreceptor differentiation. These results suggest that EPA promoted photoreceptor differentiation and rescued photoreceptors from oxidative stress-induced apoptosis through its elongation and desaturation to DHA. Our data show, for the first time, that isolated retinal neurons can synthesize DHA in culture. Docosahexaenoic acid (DHA), the major polyunsaturated fatty acid in retina photoreceptors, and its precursor, eicosapentaenoic acid (EPA) have multiple beneficial effects. Here, we show that retina neurons in vitro express the desaturase FADS2 and can synthesize DHA from EPA. Moreover, addition of EPA to these cultures protects photoreceptors from oxidative stress and promotes their differentiation through its metabolization to DHA.
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Affiliation(s)
- María Victoria Simón
- Instituto de Investigaciones Bioquímicas de Bahía Blanca (INIBIBB), Department of Biology, Biochemistry and Pharmacy, Univ Nacional del Sur (UNS)-CONICET, Bahía Blanca, Buenos Aires, Argentina
| | - Daniela L Agnolazza
- Instituto de Investigaciones Bioquímicas de Bahía Blanca (INIBIBB), Department of Biology, Biochemistry and Pharmacy, Univ Nacional del Sur (UNS)-CONICET, Bahía Blanca, Buenos Aires, Argentina
| | - Olga Lorena German
- Instituto de Investigaciones Bioquímicas de Bahía Blanca (INIBIBB), Department of Biology, Biochemistry and Pharmacy, Univ Nacional del Sur (UNS)-CONICET, Bahía Blanca, Buenos Aires, Argentina
| | - Andrés Garelli
- Instituto de Investigaciones Bioquímicas de Bahía Blanca (INIBIBB), Department of Biology, Biochemistry and Pharmacy, Univ Nacional del Sur (UNS)-CONICET, Bahía Blanca, Buenos Aires, Argentina
| | - Luis E Politi
- Instituto de Investigaciones Bioquímicas de Bahía Blanca (INIBIBB), Department of Biology, Biochemistry and Pharmacy, Univ Nacional del Sur (UNS)-CONICET, Bahía Blanca, Buenos Aires, Argentina
| | - Martin-Paul Agbaga
- Cell Biology, Univ of Oklahoma Hlth Sci Ctr, Oklahoma City, Oklahoma, USA.,Univ of Oklahoma Hlth Sci Ctr, Oklahoma City, Oklahoma, USA
| | - Robert E Anderson
- Univ of Oklahoma Hlth Sci Ctr, Oklahoma City, Oklahoma, USA.,Ophthalmology/Cell Biology, Univ of Oklahoma Hlth Sci Ctr, Oklahoma City, Oklahoma, USA
| | - Nora P Rotstein
- Instituto de Investigaciones Bioquímicas de Bahía Blanca (INIBIBB), Department of Biology, Biochemistry and Pharmacy, Univ Nacional del Sur (UNS)-CONICET, Bahía Blanca, Buenos Aires, Argentina
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26
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Cournia Z, Allen TW, Andricioaei I, Antonny B, Baum D, Brannigan G, Buchete NV, Deckman JT, Delemotte L, del Val C, Friedman R, Gkeka P, Hege HC, Hénin J, Kasimova MA, Kolocouris A, Klein ML, Khalid S, Lemieux MJ, Lindow N, Roy M, Selent J, Tarek M, Tofoleanu F, Vanni S, Urban S, Wales DJ, Smith JC, Bondar AN. Membrane Protein Structure, Function, and Dynamics: a Perspective from Experiments and Theory. J Membr Biol 2015; 248:611-40. [PMID: 26063070 PMCID: PMC4515176 DOI: 10.1007/s00232-015-9802-0] [Citation(s) in RCA: 130] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Accepted: 03/26/2015] [Indexed: 01/05/2023]
Abstract
Membrane proteins mediate processes that are fundamental for the flourishing of biological cells. Membrane-embedded transporters move ions and larger solutes across membranes; receptors mediate communication between the cell and its environment and membrane-embedded enzymes catalyze chemical reactions. Understanding these mechanisms of action requires knowledge of how the proteins couple to their fluid, hydrated lipid membrane environment. We present here current studies in computational and experimental membrane protein biophysics, and show how they address outstanding challenges in understanding the complex environmental effects on the structure, function, and dynamics of membrane proteins.
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Affiliation(s)
- Zoe Cournia
- Biomedical Research Foundation, Academy of Athens, 4 Soranou Ephessiou, 11527, Athens, Greece
| | - Toby W. Allen
- School of Applied Sciences & Health Innovations Research Institute, RMIT University, GPO Box 2476, Melbourne, Vic, 3001, Australia; and Department of Chemistry, University of California, Davis. Davis, CA 95616, USA
| | - Ioan Andricioaei
- Department of Chemistry, University of California, Irvine, CA 92697
| | - Bruno Antonny
- Institut de Pharmacologie Moléculaire et Cellulaire, Université de Nice Sophia-Antipolis and Centre National de la Recherche Scientifique, UMR 7275, 06560 Valbonne, France
| | - Daniel Baum
- Department of Visualization and Data Analysis, Zuse Institute Berlin, Takustrasse 7, D-14195 Berlin, Germany
| | - Grace Brannigan
- Center for Computational and Integrative Biology and Department of Physics, Rutgers University-Camden, Camden, NJ, USA
| | - Nicolae-Viorel Buchete
- School of Physics and Complex and Adaptive Systems Laboratory, University College Dublin, Belfield, Dublin 4, Ireland
| | | | - Lucie Delemotte
- Institute of Computational and Molecular Science, Temple University, Philadelphia, Pennsylvania 19122, United States
| | - Coral del Val
- Department of Artificial Intelligence, University of Granada, E-18071 Granada, Spain
| | - Ran Friedman
- Linnæus University, Department of Chemistry and Biomedical Sciences & Centre for Biomaterials Chemistry, 391 82 Kalmar, Sweden
| | - Paraskevi Gkeka
- Biomedical Research Foundation, Academy of Athens, 4 Soranou Ephessiou, 11527, Athens, Greece
| | - Hans-Christian Hege
- Department of Visualization and Data Analysis, Zuse Institute Berlin, Takustrasse 7, D-14195 Berlin, Germany
| | - Jérôme Hénin
- Laboratoire de Biochimie Théorique, IBPC and CNRS, Paris, France
| | - Marina A. Kasimova
- Université de Lorraine, SRSMC, UMR 7565, Vandoeuvre-lès-Nancy, F-54500, France
- Lomonosov Moscow State University, Moscow, 119991, Russian Federation
| | - Antonios Kolocouris
- Faculty of Pharmacy, Department of Pharmaceutical Chemistry, University of Athens, Panepistimioupolis-Zografou, 15771 Athens, Greece
| | - Michael L. Klein
- Institute of Computational and Molecular Science, Temple University, Philadelphia, Pennsylvania 19122, United States
| | - Syma Khalid
- Department of Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, UK
| | - M. Joanne Lemieux
- Department of Biochemistry, Faculty of Medicine & Dentistry, Membrane Protein Disease Research Group, and Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada, T6G 2H7
| | - Norbert Lindow
- Department of Visualization and Data Analysis, Zuse Institute Berlin, Takustrasse 7, D-14195 Berlin, Germany
| | - Mahua Roy
- Department of Chemistry, University of California, Irvine
| | - Jana Selent
- Research Programme on Biomedical Informatics (GRIB), Department of Experimental and Health Sciences, Universitat Pompeu Fabra, IMIM (Hospital del Mar Medical Research Institute), Dr. Aiguader 88, E-08003 Barcelona, Spain
| | - Mounir Tarek
- Université de Lorraine, SRSMC, UMR 7565, Vandoeuvre-lès-Nancy, F-54500, France
- CNRS, SRSMC, UMR 7565, Vandoeuvre-lès-Nancy, F-54500, France
| | - Florentina Tofoleanu
- School of Physics and Complex and Adaptive Systems Laboratory, University College Dublin, Belfield, Dublin 4, Ireland
| | - Stefano Vanni
- Institut de Pharmacologie Moléculaire et Cellulaire, Université de Nice Sophia-Antipolis and Centre National de la Recherche Scientifique, UMR 7275, 06560 Valbonne, France
| | - Sinisa Urban
- Johns Hopkins University School of Medicine, Howard Hughes Medical Institute, Department of Molecular Biology & Genetics, 725 N. Wolfe Street, 507 Preclinical Teaching Building, Baltimore, MD 21205, USA
| | - David J. Wales
- University Chemical Laboratories, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K
| | - Jeremy C. Smith
- Oak Ridge National Laboratory, PO BOX 2008 MS6309, Oak Ridge, TN 37831-6309, USA
| | - Ana-Nicoleta Bondar
- Theoretical Molecular Biophysics, Department of Physics, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany
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Gater DL, Saurel O, Iordanov I, Liu W, Cherezov V, Milon A. Two classes of cholesterol binding sites for the β2AR revealed by thermostability and NMR. Biophys J 2015; 107:2305-12. [PMID: 25418299 DOI: 10.1016/j.bpj.2014.10.011] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Revised: 09/19/2014] [Accepted: 10/09/2014] [Indexed: 11/24/2022] Open
Abstract
Cholesterol binding to G protein-coupled receptors (GPCRs) and modulation of their activities in membranes is a fundamental issue for understanding their function. Despite the identification of cholesterol binding sites in high-resolution x-ray structures of the ?2 adrenergic receptor (β2AR) and other GPCRs, the binding affinity of cholesterol for this receptor and exchange rates between the free and bound cholesterol remain unknown. In this study we report the existence of two classes of cholesterol binding sites in β2AR. By analyzing the β2AR unfolding temperature in lipidic cubic phase (LCP) as a function of cholesterol concentration we observed high-affinity cooperative binding of cholesterol with sub-nM affinity constant. In contrast, saturation transfer difference (STD) NMR experiments revealed the existence of a second class of cholesterol binding sites, in fast exchange on the STD NMR timescale. Titration of the STD signal as a function of cholesterol concentration provided a lower limit of 100 mM for their dissociation constant. However, these binding sites are specific for both cholesterol and β2AR, as shown with control experiments using ergosterol and a control membrane protein (KpOmpA). We postulate that this specificity is mediated by the high-affinity bound cholesterol molecules and propose the formation of transient cholesterol clusters around the high-affinity binding sites.
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Affiliation(s)
- Deborah L Gater
- Institute of Pharmacology and Structural Biology - UMR 5089, CNRS and Université de Toulouse - UPS, 205 Route de Narbonne, 31077 Toulouse, France; Khalifa University of Science, Technology and Research, P.O. Box 127788, Abu Dhabi, UAE
| | - Olivier Saurel
- Institute of Pharmacology and Structural Biology - UMR 5089, CNRS and Université de Toulouse - UPS, 205 Route de Narbonne, 31077 Toulouse, France
| | - Iordan Iordanov
- Institute of Pharmacology and Structural Biology - UMR 5089, CNRS and Université de Toulouse - UPS, 205 Route de Narbonne, 31077 Toulouse, France
| | - Wei Liu
- Department of Integrative Structural and Computational Biology, Scripps Research Institute, La Jolla, California
| | - Vadim Cherezov
- Department of Integrative Structural and Computational Biology, Scripps Research Institute, La Jolla, California.
| | - Alain Milon
- Institute of Pharmacology and Structural Biology - UMR 5089, CNRS and Université de Toulouse - UPS, 205 Route de Narbonne, 31077 Toulouse, France.
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Antonny B, Vanni S, Shindou H, Ferreira T. From zero to six double bonds: phospholipid unsaturation and organelle function. Trends Cell Biol 2015; 25:427-36. [DOI: 10.1016/j.tcb.2015.03.004] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Revised: 03/19/2015] [Accepted: 03/23/2015] [Indexed: 01/21/2023]
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Pinot M, Vanni S, Pagnotta S, Lacas-Gervais S, Payet LA, Ferreira T, Gautier R, Goud B, Antonny B, Barelli H. Lipid cell biology. Polyunsaturated phospholipids facilitate membrane deformation and fission by endocytic proteins. Science 2014; 345:693-7. [PMID: 25104391 DOI: 10.1126/science.1255288] [Citation(s) in RCA: 241] [Impact Index Per Article: 24.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Phospholipids (PLs) with polyunsaturated acyl chains are extremely abundant in a few specialized cellular organelles such as synaptic vesicles and photoreceptor discs, but their effect on membrane properties is poorly understood. Here, we found that polyunsaturated PLs increased the ability of dynamin and endophilin to deform and vesiculate synthetic membranes. When cells incorporated polyunsaturated fatty acids into PLs, the plasma membrane became more amenable to deformation by a pulling force and the rate of endocytosis was accelerated, in particular, under conditions in which cholesterol was limiting. Molecular dynamics simulations and biochemical measurements indicated that polyunsaturated PLs adapted their conformation to membrane curvature. Thus, by reducing the energetic cost of membrane bending and fission, polyunsaturated PLs may help to support rapid endocytosis.
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Affiliation(s)
- Mathieu Pinot
- Institut de Pharmacologie Moléculaire et Cellulaire, Université Nice Sophia Antipolis and CNRS, 06560 Valbonne, France. Unité Mixte de Recherche 144, Institut Curie and CNRS, F-75248 Paris, France
| | - Stefano Vanni
- Institut de Pharmacologie Moléculaire et Cellulaire, Université Nice Sophia Antipolis and CNRS, 06560 Valbonne, France
| | - Sophie Pagnotta
- Centre Commun de Microscopie Appliquée, Université Nice Sophia Antipolis, Parc Valrose, 06000 Nice, France
| | - Sandra Lacas-Gervais
- Centre Commun de Microscopie Appliquée, Université Nice Sophia Antipolis, Parc Valrose, 06000 Nice, France
| | - Laurie-Anne Payet
- Signalisation et Transports Ioniques Membranaires, Université de Poitiers and CNRS, Poitiers, France
| | - Thierry Ferreira
- Signalisation et Transports Ioniques Membranaires, Université de Poitiers and CNRS, Poitiers, France
| | - Romain Gautier
- Institut de Pharmacologie Moléculaire et Cellulaire, Université Nice Sophia Antipolis and CNRS, 06560 Valbonne, France
| | - Bruno Goud
- Unité Mixte de Recherche 144, Institut Curie and CNRS, F-75248 Paris, France
| | - Bruno Antonny
- Institut de Pharmacologie Moléculaire et Cellulaire, Université Nice Sophia Antipolis and CNRS, 06560 Valbonne, France.
| | - Hélène Barelli
- Institut de Pharmacologie Moléculaire et Cellulaire, Université Nice Sophia Antipolis and CNRS, 06560 Valbonne, France
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30
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Pawlik D, Lauterbach R, Walczak M, Hurkała J, Sherman MP. Fish-oil fat emulsion supplementation reduces the risk of retinopathy in very low birth weight infants: a prospective, randomized study. JPEN J Parenter Enteral Nutr 2013; 38:711-6. [PMID: 23963690 DOI: 10.1177/0148607113499373] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2013] [Accepted: 07/03/2013] [Indexed: 11/17/2022]
Abstract
BACKGROUND Preliminary studies suggest that fish-oil lipid emulsion given parenterally to very preterm infants reduces the severity of retinopathy (ROP) and cholestasis. METHODS Infants weighing <1250 g at birth were randomly allocated to 2 groups: an experimental group of 60 infants that received an intravenous (IV) soybean, olive oil, and fish oil emulsion, and a control group of 70 infants that was given a parenteral soybean and olive oil emulsion. Plasma and erythrocyte concentrations of docosahexaenoic acid (DHA) were determined using a high-performance liquid chromatography-mass spectrometry analysis. RESULTS Nine infants in the fish oil group required laser therapy for ROP compared with 22 infants in the standard intralipid group (risk ratio [RR], 0.48; 95% confidence interval [CI], 0.24-0.96). Three infants in the fish oil group developed cholestasis compared with 20 infants in the standard intralipid group (RR, 0.18; 95% CI, 0.055-0.56). The mean plasma DHA concentrations in treated infants were 2.9-fold higher in the fish oil group than in control infants on the 7th and 14th days of life. The mean DHA content in erythrocytes of treated infants was 4.5-fold and 2.7-fold higher compared with controls at 7 and 14 days of age. CONCLUSIONS Premature infants receiving an IV fat emulsion containing fish oil had less ROP requiring laser treatment and less cholestasis than those receiving a standard lipid emulsion. These infants also had higher plasma and erythrocyte DHA levels at 7 and 14 days, suggesting potential long-term neurodevelopmental benefits.
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Affiliation(s)
- Dorota Pawlik
- Department of Neonatology, Jagiellonian University Medical College, Kraków, Poland
| | - Ryszard Lauterbach
- Department of Neonatology, Jagiellonian University Medical College, Kraków, Poland
| | - Maria Walczak
- Department of Pharmacokinetics and Physical Pharmacy, Jagiellonian University Medical College, Kraków, Poland
| | - Joanna Hurkała
- Department of Neonatology, Jagiellonian University Medical College, Kraków, Poland
| | - Michael P Sherman
- Division of Neonatology, Department of Child Health, University of Missouri School of Medicine, Columbia, Missouri
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31
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Sánchez-Martín MJ, Ramon E, Torrent-Burgués J, Garriga P. Improved Conformational Stability of the Visual G Protein-Coupled Receptor Rhodopsin by Specific Interaction with Docosahexaenoic Acid Phospholipid. Chembiochem 2013; 14:639-44. [DOI: 10.1002/cbic.201200687] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Indexed: 11/10/2022]
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Abstract
Photoreceptors are exquisitely adapted to transform light stimuli into electrical signals that modulate neurotransmitter release. These cells are organized into several compartments including the unique outer segment (OS). Its whole function is to absorb light and transduce this signal into a change of membrane potential. Another compartment is the inner segment where much of metabolism and regulation of membrane potential takes place and that connects the OS and synapse. The synapse is the compartment where changes in membrane potentials are relayed to other neurons in the retina via release of neurotransmitter. The composition of the plasma membrane surrounding these compartments varies to accommodate their specific functions. In this chapter, we discuss the organization of the plasma membrane emphasizing the protein composition of each region as it relates to visual signaling. We also point out examples where mutations in these proteins cause visual impairment.
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Affiliation(s)
- Sheila A Baker
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.
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33
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NGF blocks polyunsaturated fatty acids biosynthesis in n−3 fatty acid-supplemented PC12 cells. Biochim Biophys Acta Mol Cell Biol Lipids 2012; 1821:1022-30. [DOI: 10.1016/j.bbalip.2012.04.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Revised: 04/19/2012] [Accepted: 04/22/2012] [Indexed: 11/19/2022]
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Sasaki T, Razak NWA, Kato N, Mukai Y. Characteristics of halorhodopsin-bacterioruberin complex from Natronomonas pharaonis membrane in the solubilized system. Biochemistry 2012; 51:2785-94. [PMID: 22369627 DOI: 10.1021/bi201876p] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Halorhodopsin is a retinal protein with a seven-transmembrane helix and acts as an inward light-driven Cl(-) pump. In this study, structural state of the solubilized halorhodopsin (NpHR) from the biomembrane of mutant strain KM-1 of Natronomonas pharaonis in nonionic detergent was investigated. A gel filtration chromatography monitored absorbances at 280 and 504 nm corresponding to the protein and a lipid soluble pigment of bacterioruberin (BR), respectively, has clearly detected an oligomer formation of the NpHRs and a complex formation between the NpHR and BR in the solubilized system. A molar ratio of NpHR:BR in the solubilized complex was close to 1:1. Further SDS-PAGE analysis of the solubilized NpHR cross-linked by 1% glutaraldehyde has revealed that the NpHR forms homotrimer in detergent system. Although this trimeric structure was stable in the presence of NaCl, it was dissociated to the monomer by the heat treatment at 45 °C in the desalted condition. The same tendency has been reported in the case of trimeric NpHR expressed heterologously on the E. coli membrane, leading to a conclusion that the change of strength of the trimeric association dependent on the ion binding is a universal feature of the NpHR. Interestingly, the trimer dissociation on the NpHR was accompanied by the complete dissociation of the BR molecule from the protein, indicated that the cavity formed by the NpHR protomers in the trimeric conformation is important for tight binding of the BR. Because the binding affinity for Cl(-) and the resistance to hydroxylamine under light illumination showed only minor differences between the NpHR in the solubilized state and that on the biomembrane, the influences of solubilization to the tertiary structure and function of the protein are thought to be minor. This NpHR-BR complex in the solubilized system has a potential to be a good model system to investigate the intermolecular interaction between the membrane protein and lipid.
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Affiliation(s)
- Takanori Sasaki
- School of Science and Technology, Meiji University, Tama-ku, Kawasaki-shi, Kanagawa 214-8571, Japan.
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Abstract
The visual pigment, rhodopsin, consists of opsin protein with 11-cis retinal chromophore, covalently bound. Light activates rhodopsin by isomerizing the chromophore to the all-trans conformation. The activated rhodopsin sets in motion a biochemical cascade that evokes an electrical response by the photoreceptor. All-trans retinal is eventually released from the opsin and reduced to vitamin A. Rod and cone photoreceptors contain vast amounts of rhodopsin, so after exposure to bright light, the concentration of vitamin A can reach relatively high levels within their outer segments. Since a retinal analog, β-ionone, is capable of activating some types of visual pigments, we tested whether vitamin A might produce a similar effect. In single-cell recordings from isolated dark-adapted salamander green-sensitive rods, exogenously applied vitamin A decreased circulating current and flash sensitivity and accelerated flash response kinetics. These changes resembled those produced by exposure of rods to steady light. Microspectrophotometric measurements showed that vitamin A accumulated in the outer segments and binding of vitamin A to rhodopsin was confirmed in in vitro assays. In addition, vitamin A improved the sensitivity of photoreceptors to ultraviolet (UV) light. Apparently, the energy of a UV photon absorbed by vitamin A transferred by a radiationless process to the 11-cis retinal chromophore of rhodopsin, which subsequently isomerized. Therefore, our results suggest that vitamin A binds to rhodopsin at an allosteric binding site distinct from the chromophore binding pocket for 11-cis retinal to activate the rhodopsin, and that it serves as a sensitizing chromophore for UV light.
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36
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Oates J, Watts A. Uncovering the intimate relationship between lipids, cholesterol and GPCR activation. Curr Opin Struct Biol 2011; 21:802-7. [DOI: 10.1016/j.sbi.2011.09.007] [Citation(s) in RCA: 185] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Revised: 09/23/2011] [Accepted: 09/29/2011] [Indexed: 11/16/2022]
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Abstract
Over the last decade, several epidemiological studies based on food frequency questionnaires suggest that omega-3 polyunsaturated fatty acids could have a protective role in reducing the onset and progression of retinal diseases. The retina has a high concentration of omega-3, particularly DHA, which optimizes fluidity of photoreceptor membranes, retinal integrity, and visual function. Furthermore, many studies demonstrated that DHA has a protective, for example antiapoptotic, role in the retina. From a nutritional point of view, it is known that western populations, particularly aged individuals, have a higher than optimal omega-6/omega-3 ratio and should enrich their diet with more fish consumption or have DHA supplementation. This paper underscores the potential beneficial effect of omega-3 fatty acids on retinal diseases.
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Buzhynskyy N, Salesse C, Scheuring S. Rhodopsin is spatially heterogeneously distributed in rod outer segment disk membranes. J Mol Recognit 2011; 24:483-9. [DOI: 10.1002/jmr.1086] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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39
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Kaya AI, Thaker TM, Preininger AM, Iverson TM, Hamm HE. Coupling efficiency of rhodopsin and transducin in bicelles. Biochemistry 2011; 50:3193-203. [PMID: 21375271 DOI: 10.1021/bi200037j] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
G protein coupled receptors (GPCRs) can be activated by various extracellular stimuli, including hormones, peptides, odorants, neurotransmitters, nucleotides, or light. After activation, receptors interact with heterotrimeric G proteins and catalyze GDP release from the Gα subunit, the rate limiting step in G protein activation, to form a high affinity nucleotide-free GPCR-G protein complex. In vivo, subsequent GTP binding reduces affinity of the Gα protein for the activated receptor. In this study, we investigated the biochemical and structural characteristics of the prototypical GPCR, rhodopsin, and its signaling partner, transducin (G(t)), in bicelles to better understand the effects of membrane composition on high affinity complex formation, stability, and receptor mediated nucleotide release. Our results demonstrate that the high-affinity complex (rhodopsin-G(t)(empty)) forms more readily and has dramatically increased stability when rhodopsin is integrated into bicelles of a defined composition. We increased the half-life of functional complex to 1 week in the presence of negatively charged phospholipids. These data suggest that a membrane-like structure is an important contributor to the formation and stability of functional receptor-G protein complexes and can extend the range of studies that investigate properties of these complexes.
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Affiliation(s)
- Ali I Kaya
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-6600, United States
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Lien EL, Hammond BR. Nutritional influences on visual development and function. Prog Retin Eye Res 2011; 30:188-203. [PMID: 21296184 DOI: 10.1016/j.preteyeres.2011.01.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 01/07/2011] [Accepted: 01/24/2011] [Indexed: 02/07/2023]
Abstract
Experiments conducted on many different species reveal a fundamental paradox about the vertebrate eye; it is damaged by its own operation. This vulnerability stems from the need to respond to visible light, often actinic, but also from the intrinsic metabolic and structural state of the eye's internal structures. Photoreceptor outer segments, for instance, have high concentrations of diet-derived long-chain polyunsaturated fatty acids and these membrane lipids are highly prone to peroxidation due to the high oxygen tension of the outer retina. Such a high diathesis for damage would be catastrophic if it were not balanced by an equally impressive system for responding to such stressors. The retina (and to a lesser extent the crystalline lens), for instance, is especially rich in dietary antioxidants such as vitamin E, vitamin C and the macular carotenoids (lutein and zeaxanthin) putatively to retard light-induced oxidative damage. The nutrients that support both essential function (e.g., retinal, the vitamin form of vitamin A, in photopigment) and protection operate in a highly integrated manner. For instance, Vitamin E is a lipophillic chain-breaking anti-oxidant (protecting DHA-rich outer segment membranes) that regenerates itself through reaction with vitamin C (a primary anti-oxidant against aqueous radicals) and is spatially distributed in complement with the carotenoids lutein and zeaxanthin. Nor are these interactions relegated to simply providing protection and the basic elements needed for transduction. Macular lutein and zeaxanthin, for example, improve visual performance (e.g., reduce glare disability and discomfort, speed photostress recovery, and enhance chromatic contrast) through purely optical means (by absorbing short-wave light anterior to the foveal cones). The vulnerability of the eye to exogenous insult, and the sensitivity of the eye to dietary components, is not static: infants have more vulnerable retinas due to clearer lenses and higher metabolic activity; the elderly are more vulnerable due to such factors as increased inflammatory stress and a higher content of photosensitizers (such as lipofuscin) creating cascading oxidative effects. Hence, optimal dietary prophylaxis changes as the eye ages. The eye, perhaps more than most other biological structures, has evolved an exquisite and shifting sensitivity to dietary intake throughout the lifespan, not just for its basic operation (e.g., Vitamin A for transduction), but also for its very preservation.
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Affiliation(s)
- Eric L Lien
- Department of Food Science and Human Nutrition, University of Illinois, Urbana, IL 61801, USA
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41
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Schultz ZD. Raman Spectroscopic Imaging of Cholesterol and Docosahexaenoic Acid Distribution in the Retinal Rod Outer Segment. Aust J Chem 2011; 64:611-616. [PMID: 21799539 DOI: 10.1071/ch11019] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Raman vibrational spectroscopic imaging was performed on retinal rod cells isolated from bullfrogs (Rana catesbeiana). The Raman spectra enable determination of the lipid and protein rich rod outer segment (ROS) from the nucleus and inner segment of the cell. Peak fitting analysis of spectra obtained from individual rod photoreceptor cells show characteristic vibrational modes that can be associated with cholesterol and docosahexaenoic acid containing lipids. These results provide direct observations of biomolecular gradients in the rod photoreceptor cells, which, thus far, have been based on indirect detergent extracts and histochemical analysis with indicators such as filipin. The detected biomolecules are associated with regulation of the integral membrane protein rhodopsin, and methods capable direct observation of these biomolecules offer new routes to exploring their role in the regulation of cellular processes.
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Affiliation(s)
- Zachary D Schultz
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46566
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Soubias O, Teague WE, Hines KG, Mitchell DC, Gawrisch K. Contribution of membrane elastic energy to rhodopsin function. Biophys J 2010; 99:817-24. [PMID: 20682259 DOI: 10.1016/j.bpj.2010.04.068] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2009] [Revised: 04/16/2010] [Accepted: 04/23/2010] [Indexed: 11/16/2022] Open
Abstract
We considered the issue of whether shifts in the metarhodopsin I (MI)-metarhodopsin II (MII) equilibrium from lipid composition are fully explicable by differences in bilayer curvature elastic stress. A series of six lipids with known spontaneous radii of monolayer curvature and bending elastic moduli were added at increasing concentrations to the matrix lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and the MI-MII equilibrium measured by flash photolysis followed by recording UV-vis spectra. The average area-per-lipid molecule and the membrane hydrophobic thickness were derived from measurements of the (2)H NMR order parameter profile of the palmitic acid chain in POPC. For the series of ethanolamines with different levels of headgroup methylation, shifts in the MI-MII equilibrium correlated with changes in membrane elastic properties as expressed by the product of spontaneous radius of monolayer curvature, bending elastic modulus, and lateral area per molecule. However, for the entire series of lipids, elastic energy explained the shifts only partially. Additional contributions correlated with the capability of the ethanolamine headgroups to engage in hydrogen bonding with the protein, independent of the state of ethanolamine methylation, with introduction of polyunsaturated sn-2 hydrocarbon chains, and with replacement of the palmitic acid sn-1 chains by oleic acid. The experiments point to the importance of interactions of rhodopsin with particular lipid species in the first layer of lipids surrounding the protein as well as to membrane elastic stress in the lipid-protein domain.
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Affiliation(s)
- Olivier Soubias
- Laboratory of Membrane Biochemistry and Biophysics, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland, USA
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Abstract
Activation of GPCRs (G-protein-coupled receptors) leads to conformational changes that ultimately initiate signal transduction. Activated GPCRs transiently combine with and activate heterotrimeric G-proteins resulting in GTP replacement of GDP on the G-protein alpha subunit. Both the detailed structural changes essential for productive GDP/GTP exchange on the G-protein alpha subunit and the structure of the GPCR-G-protein complex itself have yet to be elucidated. Nevertheless, transient GPCR-G-protein complexes can be trapped by nucleotide depletion, yielding an empty-nucleotide G-protein-GPCR complex that can be isolated. Whereas early biochemical studies indicated formation of a complex between G-protein and activated receptor only, more recent results suggest that G-protein can bind to pre-activated states of receptor or even couple transiently to non-activated receptor to facilitate rapid responses to stimuli. Efficient and reproducible formation of physiologically relevant, conformationally homogenous GPCR-G-protein complexes is a prerequisite for structural studies designed to address these possibilities.
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44
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Agbaga MP, Mandal MNA, Anderson RE. Retinal very long-chain PUFAs: new insights from studies on ELOVL4 protein. J Lipid Res 2010; 51:1624-42. [PMID: 20299492 DOI: 10.1194/jlr.r005025] [Citation(s) in RCA: 122] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Compared with other mammalian tissues, retina is highly enriched in PUFA. Long-chain PUFA (LC-PUFA; C18-C24) are essential FAs that are enriched in the retina and are necessary for maintenance of normal retinal development and function. The retina, brain, and sperm also contain very LC-PUFA (VLC-PUFA; >C24). Although VLC-PUFA were discovered more than two decades ago, very little is known about their biosynthesis and functional roles in the retina. This is due mainly to intrinsic difficulties associated with working on these unusually long polyunsaturated hydrocarbon chains and their existence in small amounts. Recent studies on the FA elongase elongation of very long chain fatty acids-4 (ELOVL4) protein, however, suggest that VLC-PUFA probably play some uniquely important roles in the retina as well as the other tissues. Mutations in the ELOVL4 gene are found in patients with autosomal dominant Stargardt disease. Here, we review the recent literature on VLC-PUFA with special emphasis on the elongases responsible for their synthesis. We focus on a novel elongase, ELOVL4, involved in the synthesis of VLC-PUFA, and the importance of these FAs in maintaining the structural and functional integrity of retinal photoreceptors.
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Affiliation(s)
- Martin-Paul Agbaga
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
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45
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Khelashvili G, Grossfield A, Feller SE, Pitman MC, Weinstein H. Structural and dynamic effects of cholesterol at preferred sites of interaction with rhodopsin identified from microsecond length molecular dynamics simulations. Proteins 2009; 76:403-17. [PMID: 19173312 PMCID: PMC4101808 DOI: 10.1002/prot.22355] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
An unresolved question about GPCR function is the role of membrane components in receptor stability and activation. In particular, cholesterol is known to affect the function of membrane proteins, but the details of its effect on GPCRs are still elusive. Here, we describe how cholesterol modulates the behavior of the TM1-TM2-TM7-helix 8(H8) functional network that comprises the highly conserved NPxxY(x)(5,6)F motif, through specific interactions with the receptor. The inferences are based on the analysis of microsecond length molecular dynamics (MD) simulations of rhodopsin in an explicit membrane environment. Three regions on the rhodopsin exhibit the highest cholesterol density throughout the trajectory: the extracellular end of TM7, a location resembling the high-density sterol area from the electron microscopy data; the intracellular parts of TM1, TM2, and TM4, a region suggested as the cholesterol binding site in the recent X-ray crystallography data on beta(2)-adrenergic GPCR; and the intracellular ends of TM2-TM3, a location that was categorized as the high cholesterol density area in multiple independent 100 ns MD simulations of the same system. We found that cholesterol primarily affects specific local perturbations of the helical TM domains such as the kinks in TM1, TM2, and TM7. These local distortions, in turn, relate to rigid-body motions of the TMs in the TM1-TM2-TM7-H8 bundle. The specificity of the effects stems from the nonuniform distribution of cholesterol around the protein. Through correlation analysis we connect local effects of cholesterol on structural perturbations with a regulatory role of cholesterol in the structural rearrangements involved in GPCR function.
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Affiliation(s)
- George Khelashvili
- Department of Physiology and Biophysics, Weill Medical College of Cornell University, New York, New York 10021, USA.
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Jastrzebska B, Goc A, Golczak M, Palczewski K. Phospholipids are needed for the proper formation, stability, and function of the photoactivated rhodopsin-transducin complex. Biochemistry 2009; 48:5159-70. [PMID: 19413332 DOI: 10.1021/bi900284x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Heterotrimeric G proteins become activated after they form a catalytically active complex with activated G protein-coupled receptors (GPCRs) and GTP replaces GDP on the G protein alpha-subunit. This transient coupling can be stabilized by nucleotide depletion, resulting in an empty-nucleotide G protein-GPCR complex. Efficient and reproducible formation of conformationally homogeneous GPCR-Gt complexes is a prerequisite for structural studies. Herein, we report isolation conditions that enhance the stability and preserve the activity and proper stoichiometry of productive complexes between the purified prototypical GPCR, rhodopsin (Rho), and the rod cell-specific G protein, transducin (Gt). Binding of purified Gt to photoactivated Rho (Rho*) in n-dodecyl beta-D-maltoside (DDM) examined by gel filtration chromatography was generally modest, and purified complexes provided heterogeneous ratios of protein components, most likely because of excess detergent. Rho*-Gt complex stability and activity were greatly increased by addition of phospholipids such as DOPC, DOPE, and DOPS and asolectin to detergent-containing solutions of these proteins. In contrast, native Rho*-Gt complexes purified directly from light-exposed bovine ROS membranes by sucrose gradient centrifugation exhibited improved stability and the expected 2:1 stoichiometry between Rho* and Gt. These results strongly indicate a lipid requirement for stable complex formation in which the likely oligomeric structure of Rho provides a superior platform for coupling to Gt, and phospholipids likely form a matrix to which Gt can anchor through its myristoyl and farnesyl groups. Our findings also demonstrate that the choice of detergent and purification method is critical for obtaining highly purified, stable, and active complexes with appropriate stoichiometry between GPCRs and G proteins needed for structural studies.
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Affiliation(s)
- Beata Jastrzebska
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4965, USA
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Brown MF, Martínez-Mayorga K, Nakanishi K, Salgado GFJ, Struts AV. Retinal conformation and dynamics in activation of rhodopsin illuminated by solid-state H NMR spectroscopy. Photochem Photobiol 2009; 85:442-53. [PMID: 19267870 DOI: 10.1111/j.1751-1097.2008.00510.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Solid-state NMR spectroscopy gives a powerful avenue for investigating G protein-coupled receptors and other integral membrane proteins in a native-like environment. This article reviews the use of solid-state (2)H NMR to study the retinal cofactor of rhodopsin in the dark state as well as the meta I and meta II photointermediates. Site-specific (2)H NMR labels have been introduced into three regions (methyl groups) of retinal that are crucially important for the photochemical function of rhodopsin. Despite its phenomenal stability (2)H NMR spectroscopy indicates retinal undergoes rapid fluctuations within the protein binding cavity. The spectral lineshapes reveal the methyl groups spin rapidly about their three-fold (C(3)) axes with an order parameter for the off-axial motion of SC(3) approximately 0.9. For the dark state, the (2)H NMR structure of 11-cis-retinal manifests torsional twisting of both the polyene chain and the beta-ionone ring due to steric interactions of the ligand and the protein. Retinal is accommodated within the rhodopsin binding pocket with a negative pretwist about the C11=C12 double bond. Conformational distortion explains its rapid photochemistry and reveals the trajectory of the 11-cis to trans isomerization. In addition, (2)H NMR has been applied to study the retinylidene dynamics in the dark and light-activated states. Upon isomerization there are drastic changes in the mobility of all three methyl groups. The relaxation data support an activation mechanism whereby the beta-ionone ring of retinal stays in nearly the same environment, without a large displacement of the ligand. Interactions of the beta-ionone ring and the retinylidene Schiff base with the protein transmit the force of the retinal isomerization. Solid-state (2)H NMR thus provides information about the flow of energy that triggers changes in hydrogen-bonding networks and helix movements in the activation mechanism of the photoreceptor.
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Affiliation(s)
- Michael F Brown
- Department of Chemistry, University of Arizona, Tucson, AZ, USA.
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48
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Turner GJ, Chittiboyina S, Pohren L, Hines KG, Correia JJ, Mitchell DC. The bacteriorhodopsin carboxyl-terminus contributes to proton recruitment and protein stability. Biochemistry 2009; 48:1112-22. [PMID: 19140737 DOI: 10.1021/bi801799j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We examined functional and structural roles for the bacteriorhodopsin (bR) carboxyl-terminus. The extramembranous and intracellular carboxyl-terminus was deleted by insertion of premature translation stop codons. Deletion of the carboxyl-terminus had no effect on purple membrane (PM) lattice dimensions, sheet size, or the electrogenic environment of the ground-state chromophore. Removal of the distal half of the carboxyl-terminus had no effect on light-activated proton pumping, however, truncation of the entire carboxyl-terminus accelerated the rates of M-state decay and proton uptake approximately 3.7-fold and severely distorted the kinetics of proton uptake. Differential scanning calorimetry (DSC) and SDS denaturation demonstrated that removal of the carboxyl-terminus decreased protein stability. The DSC melting temperature was lowered by 6 degrees C and the calorimetric enthalpy reduced by 50% following removal of the carboxyl-terminus. Over the time range of milliseconds to hours at least 3 phases were required to describe the SDS denaturation kinetics for each bR construction. The fastest phases were indistinguishable for all bR's, and reflected PM solubilization. At pH 7.4, 20 degrees C, and in 0.3% SDS (w/v) the half-times of bR denaturation were 19.2 min for the wild-type, 12.0 min for the half-truncation and 3.6 min for the full-truncation. Taken together the results of this study suggest that the bR ground state exhibits two "domains" of stability: (1) a core chromophore binding pocket domain that is insensitive to carboxyl-terminal interactions and (2) the surrounding helical bundle whose contributions to protein stability and proton pumping are influenced by long-range interactions with the extramembranous carboxyl-terminus.
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Affiliation(s)
- George J Turner
- Department of Chemistry and Biochemistry, Seton Hall University, South Orange, New Jersey 07079, USA.
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49
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Soubias O, Niu SL, Mitchell DC, Gawrisch K. Lipid-rhodopsin hydrophobic mismatch alters rhodopsin helical content. J Am Chem Soc 2008; 130:12465-71. [PMID: 18712874 DOI: 10.1021/ja803599x] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The ability of photoactivated rhodopsin to achieve the enzymatically active metarhodopsin II conformation is exquisitely sensitive to bilayer hydrophobic thickness. The sensitivity of rhodopsin to the lipid matrix has been explained by the hydrophobic matching theory, which predicts that lipid bilayers adjust elastically to the hydrophobic length of transmembrane helices. Here, we examined if bilayer thickness adjusts to the length of the protein or if the protein alters its conformation to adapt to the bilayer. Purified bovine rhodopsin was reconstituted into a series of mono-unsaturated phosphatidylcholines with 14-20 carbons per hydrocarbon chain. Changes of hydrocarbon chain length were measured by (2)H NMR, and protein helical content was quantified by synchrotron radiation circular dichroism and conventional circular dichroism. Experiments were conducted on dark-adapted rhodopsin, the photo-intermediates metarhodopsin I/II/III, and opsin. Changes of bilayer thickness upon rhodopsin incorporation and photoactivation were mostly absent. In contrast, the helical content of rhodopsin increased with membrane hydrophobic thickness. Helical content did not change measurably upon photoactivation. The increases of bilayer thickness and helicity of rhodopsin are accompanied by higher metarhodopsin II/metarhodopsin I ratios, faster rates of metarhodopsin II formation, an increase of tryptophan fluorescence, and higher temperatures of rhodopsin denaturation. The data suggest a surprising adaptability of this G protein-coupled membrane receptor to properties of the lipid matrix.
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Affiliation(s)
- Olivier Soubias
- Laboratory of Membrane Biochemistry and Biophysics, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland 20892, USA
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50
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Wensel TG. Signal transducing membrane complexes of photoreceptor outer segments. Vision Res 2008; 48:2052-61. [PMID: 18456304 DOI: 10.1016/j.visres.2008.03.010] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2008] [Revised: 03/17/2008] [Accepted: 03/19/2008] [Indexed: 11/25/2022]
Abstract
Signal transduction in outer segments of vertebrate photoreceptors is mediated by a series of reactions among multiple polypeptides that form protein-protein complexes within or on the surface of the disk and plasma membranes. The individual components in the activation reactions include the photon receptor rhodopsin and the products of its absorption of light, the three subunits of the G protein, transducin, the four subunits of the cGMP phosphodiesterase, PDE6 and the four subunits of the cGMP-gated cation channel. Recovery involves membrane complexes with additional polypeptides including the Na(+)/Ca(2+), K(+) exchanger, NCKX2, rhodopsin kinases RK1 and RK7, arrestin, guanylate cyclases, guanylate cyclase activating proteins, GCAP1 and GCAP2, and the GTPase accelerating complex of RGS9-1, G(beta5L), and membrane anchor R9AP. Modes of membrane binding by these polypeptides include transmembrane helices, fatty acyl or isoprenyl modifications, polar interactions with lipid head groups, non-polar interactions of hydrophobic side chains with lipid hydrocarbon phase, and both polar and non-polar protein-protein interactions. In the course of signal transduction, complexes among these polypeptides form and dissociate, and undergo structural rearrangements that are coupled to their interactions with and catalysis of reactions by small molecules and ions, including guanine nucleotides, ATP, Ca(2+), Mg(2+), and lipids. The substantial progress that has been made in understanding the composition and function of these complexes is reviewed, along with the more preliminary state of our understanding of the structures of these complexes and the challenges and opportunities that present themselves for deepening our understanding of these complexes, and how they work together to convert a light signal into an electrical signal.
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Affiliation(s)
- Theodore G Wensel
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
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