1
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Higa N, Hayashi T, Mizobuchi K, Iwasa M, Kubota S, Kuniyoshi K, Kameya S, Kondo H, Kondo M, Nakano T. A novel RPE65 variant p.(Ala391Asp) in Leber congenital amaurosis: a case report and literature review in Japan. Front Med (Lausanne) 2024; 11:1442107. [PMID: 39359914 PMCID: PMC11446184 DOI: 10.3389/fmed.2024.1442107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2024] [Accepted: 09/02/2024] [Indexed: 10/04/2024] Open
Abstract
Introduction In Japan, inherited retinal dystrophy caused by biallelic variants of the RPE65 gene is exceedingly rare. The purpose of this study was to describe a Japanese male patient with a novel variant in RPE65 associated with Leber congenital amaurosis (LCA). Case report The patient, diagnosed with LCA, exhibited infantile nystagmus and reported experiencing night blindness since early childhood. At 27 years of age, the patient underwent an ophthalmologically evaluation. Corrected visual acuity was Snellen equivalent 20/133 in the right eye and Snellen equivalent 20/100 in the left eye. Fundus examination revealed alterations in the retinal pigment epithelium characterized by hypopigmentation and narrowing of retinal vessels. Fundus autofluorescence imaging demonstrated a generally diminished autofluorescent signal. Full-field electroretinography identified a generalized dysfunction of both rod and cone systems in each eye. Whole exome sequencing identified a novel missense variant in RPE65 (NM_000329.3): c.1172C > A p.(Ala391Asp), which was classified as pathogenic, as well as a recurrent variant p.(Arg515Trp). Conclusion This study provides valuable insights into the genotype-phenotype correlation of RPE65-associated LCA in Japanese patients, with critical implications for enhanced diagnostic accuracy and informed therapeutic decisions.
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Affiliation(s)
- Natsuki Higa
- Department of Ophthalmology, Katsushika Medical Center, The Jikei University School of Medicine, Tokyo, Japan
| | - Takaaki Hayashi
- Department of Ophthalmology, Katsushika Medical Center, The Jikei University School of Medicine, Tokyo, Japan
- Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan
| | - Kei Mizobuchi
- Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan
| | - Maki Iwasa
- Department of Ophthalmology, Shiga University of Medical Science, Otsu, Japan
| | | | - Kazuki Kuniyoshi
- Department of Ophthalmology, Kindai University Faculty of Medicine, Osaka-sayama, Japan
| | | | - Hiroyuki Kondo
- Department of Ophthalmology, University of Occupational and Environmental Health, Fukuoka, Japan
| | - Mineo Kondo
- Department of Ophthalmology, Mie University Graduate School of Medicine, Tsu City, Japan
| | - Tadashi Nakano
- Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan
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2
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Solano YJ, Everett MP, Dang KS, Abueg J, Kiser PD. Carotenoid cleavage enzymes evolved convergently to generate the visual chromophore. Nat Chem Biol 2024; 20:779-788. [PMID: 38355721 PMCID: PMC11142922 DOI: 10.1038/s41589-024-01554-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Accepted: 01/12/2024] [Indexed: 02/16/2024]
Abstract
The retinal light response in animals originates from the photoisomerization of an opsin-coupled 11-cis-retinaldehyde chromophore. This visual chromophore is enzymatically produced through the action of carotenoid cleavage dioxygenases. Vertebrates require two carotenoid cleavage dioxygenases, β-carotene oxygenase 1 and retinal pigment epithelium 65 (RPE65), to form 11-cis-retinaldehyde from carotenoid substrates, whereas invertebrates such as insects use a single enzyme known as Neither Inactivation Nor Afterpotential B (NinaB). RPE65 and NinaB couple trans-cis isomerization with hydrolysis and oxygenation, respectively, but the mechanistic relationship of their isomerase activities remains unknown. Here we report the structure of NinaB, revealing details of its active site architecture and mode of membrane binding. Structure-guided mutagenesis studies identify a residue cluster deep within the NinaB substrate-binding cleft that controls its isomerization activity. Our data demonstrate that isomerization activity is mediated by distinct active site regions in NinaB and RPE65-an evolutionary convergence that deepens our understanding of visual system diversity.
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Affiliation(s)
- Yasmeen J Solano
- Department of Physiology and Biophysics, University of California Irvine School of Medicine, Irvine, CA, USA
| | - Michael P Everett
- Department of Physiology and Biophysics, University of California Irvine School of Medicine, Irvine, CA, USA
- Research Service, VA Long Beach Healthcare System, Long Beach, CA, USA
| | - Kelly S Dang
- Department of Physiology and Biophysics, University of California Irvine School of Medicine, Irvine, CA, USA
| | - Jude Abueg
- Department of Physiology and Biophysics, University of California Irvine School of Medicine, Irvine, CA, USA
| | - Philip D Kiser
- Department of Physiology and Biophysics, University of California Irvine School of Medicine, Irvine, CA, USA.
- Research Service, VA Long Beach Healthcare System, Long Beach, CA, USA.
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California Irvine School of Medicine, Irvine, CA, USA.
- Department of Clinical Pharmacy Practice, University of California Irvine School of Pharmacy and Pharmaceutical Sciences, Irvine, CA, USA.
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3
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Stepanova A, Ogorodova N, Kadyshev V, Shchagina O, Kutsev S, Polyakov A. A Molecular Genetic Analysis of RPE65-Associated Forms of Inherited Retinal Degenerations in the Russian Federation. Genes (Basel) 2023; 14:2056. [PMID: 38002999 PMCID: PMC10671290 DOI: 10.3390/genes14112056] [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: 09/13/2023] [Revised: 10/26/2023] [Accepted: 11/01/2023] [Indexed: 11/26/2023] Open
Abstract
Pathogenic variants in the RPE65 gene cause the only known form of inherited retinal degenerations (IRDs) that are prone to gene therapy. The current study is aimed at the evaluation of the prevalence of RPE65-associated retinopathy in the Russian Federation, the characterization of known variants in the RPE65 gene, and the establishment of the specificities of the mutation spectrum in Russian patients. METHODS The analysis was carried out on blood samples obtained from 1053 non-related IRDs patients. The analysis, which consisted of 211 genes, was carried out based on the method of massive parallel sequencing (MPS) for all probands. Variant validation, as well as biallelic status verification, were carried out using direct automated Sanger sequencing. The number of copies of RPE65 exons 1-14 was analyzed with quantitative MLPA using an MRC-Holland SALSA MLPA probemix. RESULTS Out of 1053 non-related patients, a molecular genetic diagnosis of IRDs has been confirmed in 474 cases, including 25 (5.3%) patients with RPE65-associated retinopathy. We detected 26 variants in the RPE65 gene, nine of which have not been previously described in the literature. The most common mutations in the Russian population were c.304G>T/p.(Glu102*), c.370C>T/p.(Arg124*), and c.272G>A/p.(Arg91Gln), which comprised 41.8% of all affected chromosomes. CONCLUSIONS The current study shows that pathogenic variants in the RPE65 gene contribute significantly to the pathogenesis of IRDs and comprise 5.3% of all patients with a confirmed molecular genetic diagnosis. This study allowed for the formation of a cohort for target therapy of the disorder; such therapy has already been carried out for some patients.
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Affiliation(s)
- Anna Stepanova
- Research Centre for Medical Genetics, Moscow 115478, Russia
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4
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Uppal S, Poliakov E, Gentleman S, Redmond TM. The Amphipathic Helix in Visual Cycle Proteins: A Review. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1415:533-537. [PMID: 37440083 PMCID: PMC11299856 DOI: 10.1007/978-3-031-27681-1_78] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/14/2023]
Abstract
The visual cycle is a complex biological process that involves the sequential action of proteins in the retinal pigment epithelial (RPE) cells and photoreceptors to modify and shuttle visual retinoids. A majority of the visual cycle proteins are membrane proteins, either integral or peripheral membrane proteins. Despite significant progress in understanding their physiological function, very limited structural information is available for the visual cycle proteins. Moreover, the mechanism of membrane interaction is not yet clear in all cases. Here, we demonstrate the presence of an amphipathic helix in selected RPE visual cycle proteins, using in silico tools, and highlight their role in membrane association and function.
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Affiliation(s)
- Sheetal Uppal
- Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, MD, USA
| | - Eugenia Poliakov
- Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, MD, USA
| | - Susan Gentleman
- Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, MD, USA
| | - T Michael Redmond
- Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, MD, USA.
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5
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Poli G, Barravecchia I, Demontis GC, Sodi A, Saba A, Rizzo S, Macchia M, Tuccinardi T. Predicting potentially pathogenic effects of hRPE65 missense mutations: a computational strategy based on molecular dynamics simulations. J Enzyme Inhib Med Chem 2022; 37:1765-1772. [PMID: 35726567 PMCID: PMC9225791 DOI: 10.1080/14756366.2022.2090547] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
The human retinal pigment epithelium-specific 65-kDa protein (hRPE65) plays a crucial role within the retinoid visual cycle and several mutations affecting either its expression level or its enzymatic function are associated with inherited retinal diseases such as Retinitis Pigmentosa. The gene therapy product voretigene neparvovec (Luxturna) has been recently approved for treating hereditary retinal dystrophies; however, the treatment is currently accessible only to patients presenting confirmed biallelic mutations that severely impair hRPE65 function, and many reported hRPE65 missense mutations lack sufficient evidences for proving their pathogenicity. In this context, we developed a computational approach aimed at evaluating the potential pathogenic effect of hRPE65 missense variants located on the dimerisation domain of the protein. The protocol evaluates how mutations may affect folding and conformation stability of this protein region, potentially helping clinicians to evaluate the eligibility for gene therapy of patients diagnosed with this type of hRPE65 variant of uncertain significance.
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Affiliation(s)
- Giulio Poli
- Department of Pharmacy, University of Pisa, Pisa, Italy
| | - Ivana Barravecchia
- Department of Pharmacy, University of Pisa, Pisa, Italy.,Institute of Life Sciences, Scuola Superiore Sant'Anna, Pisa, Italy
| | | | - Andrea Sodi
- Department of Neurosciences, Psychology, Drug Research and Child Health Eye Clinic, University of Florence, AOU Careggi, Florence, Italy
| | - Alessandro Saba
- Department of Surgical Pathology, Molecular Medicine and of the Critical Area, University of Pisa, Pisa, Italy
| | - Stanislao Rizzo
- Ophthalmology Unit, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy.,Catholic University Sacro Cuore, Rome, Italy.,Consiglio Nazionale delle Ricerche, Istituto di Neuroscienze, Pisa, Italy
| | - Marco Macchia
- Department of Pharmacy, University of Pisa, Pisa, Italy
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6
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Uppal S, Liu T, Galvan E, Gomez F, Tittley T, Poliakov E, Gentleman S, Redmond TM. An inducible amphipathic α-helix mediates subcellular targeting and membrane binding of RPE65. Life Sci Alliance 2022; 6:6/1/e202201546. [PMID: 36265895 PMCID: PMC9585964 DOI: 10.26508/lsa.202201546] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Revised: 09/27/2022] [Accepted: 09/28/2022] [Indexed: 11/24/2022] Open
Abstract
RPE65 retinol isomerase is an indispensable player in the visual cycle between the vertebrate retina and RPE. Although membrane association is critical for RPE65 function, its mechanism is not clear. Residues 107-125 are believed to interact with membranes but are unresolved in all RPE65 crystal structures, whereas palmitoylation at C112 also plays a role. We report the mechanism of membrane recognition and binding by RPE65. Binding of aa107-125 synthetic peptide with membrane-mimicking micellar surfaces induces transition from unstructured loop to amphipathic α-helical (AH) structure but this transition is automatic in the C112-palmitoylated peptide. We demonstrate that the AH significantly affects palmitoylation level, membrane association, and isomerization activity of RPE65. Furthermore, aa107-125 functions as a membrane sensor and the AH as a membrane-targeting motif. Molecular dynamic simulations clearly show AH-membrane insertion, supporting our experimental findings. Collectively, these studies allow us to propose a working model for RPE65-membrane binding, and to provide a novel role for cysteine palmitoylation.
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Affiliation(s)
| | | | | | | | | | | | | | - T Michael Redmond
- Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, MD, USA
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7
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Kiser PD. Retinal pigment epithelium 65 kDa protein (RPE65): An update. Prog Retin Eye Res 2021; 88:101013. [PMID: 34607013 PMCID: PMC8975950 DOI: 10.1016/j.preteyeres.2021.101013] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Revised: 09/21/2021] [Accepted: 09/24/2021] [Indexed: 12/21/2022]
Abstract
Vertebrate vision critically depends on an 11-cis-retinoid renewal system known as the visual cycle. At the heart of this metabolic pathway is an enzyme known as retinal pigment epithelium 65 kDa protein (RPE65), which catalyzes an unusual, possibly biochemically unique, reaction consisting of a coupled all-trans-retinyl ester hydrolysis and alkene geometric isomerization to produce 11-cis-retinol. Early work on this isomerohydrolase demonstrated its membership to the carotenoid cleavage dioxygenase superfamily and its essentiality for 11-cis-retinal production in the vertebrate retina. Three independent studies published in 2005 established RPE65 as the actual isomerohydrolase instead of a retinoid-binding protein as previously believed. Since the last devoted review of RPE65 enzymology appeared in this journal, major advances have been made in a number of areas including our understanding of the mechanistic details of RPE65 isomerohydrolase activity, its phylogenetic origins, the relationship of its membrane binding affinity to its catalytic activity, its role in visual chromophore production for rods and cones, its modulation by macromolecules and small molecules, and the involvement of RPE65 mutations in the development of retinal diseases. In this article, I will review these areas of progress with the goal of integrating results from the varied experimental approaches to provide a comprehensive picture of RPE65 biochemistry. Key outstanding questions that may prove to be fruitful future research pursuits will also be highlighted.
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Affiliation(s)
- Philip D Kiser
- Research Service, VA Long Beach Healthcare System, Long Beach, CA, 90822, USA; Department of Physiology & Biophysics, University of California, Irvine School of Medicine, Irvine, CA, 92697, USA; Department of Ophthalmology and Center for Translational Vision Research, Gavin Herbert Eye Institute, University of California, Irvine School of Medicine, Irvine, CA, 92697, USA.
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8
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Lopez-Rodriguez R, Lantero E, Blanco-Kelly F, Avila-Fernandez A, Martin Merida I, Del Pozo-Valero M, Perea-Romero I, Zurita O, Jiménez-Rolando B, Swafiri ST, Riveiro-Alvarez R, Trujillo-Tiebas MJ, Carreño Salas E, García-Sandoval B, Corton M, Ayuso C. RPE65-related retinal dystrophy: Mutational and phenotypic spectrum in 45 affected patients. Exp Eye Res 2021; 212:108761. [PMID: 34492281 DOI: 10.1016/j.exer.2021.108761] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Revised: 08/27/2021] [Accepted: 09/01/2021] [Indexed: 11/27/2022]
Abstract
INTRODUCTION Biallelic pathogenic RPE65 variants are related to a spectrum of clinically overlapping inherited retinal dystrophies (IRD). Most affected individuals progress to severe disease, with 50% of patients becoming legally blind by 20 years of age. Deeper knowledge of the mutational spectrum and the phenotype-genotype correlation in RPE65-related IRD is needed. PATIENTS AND METHODS Forty-five affected subjects from 27 unrelated families with a clinical diagnosis of RPE65-related IRD were included. Clinical evaluation consisted of self-reported ophthalmological history and objective ophthalmological examination. Patients' genotype was classified according to variant class (truncating or missense) or to variant location at different protein domains. The main phenotypic outcome measure was age at onset (AAO) of symptomatic disease and a Kaplan-Meier analysis of disease symptom event-free survival was performed. RESULTS Twenty-nine different RPE65 variants were identified in our cohort, 7 of them novel. Patients carrying two missense alleles showed a later disease onset than those with 1 or 2 truncating variants (log-rank test p <0.05). While 60% of patients carrying a missense/missense genotype presented symptoms before or during the first year of life, almost all patients with at least 1 truncating allele (91%) had an AAO ≤1 year (p <0.05). CONCLUSION Our findings suggest an association between the type of RPE65 variant carried and AAO. These findings provide useful data on RPE65-associated IRD phenotypes and may help improve clinical and therapeutic management of these patients.
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Affiliation(s)
- Rosario Lopez-Rodriguez
- Department of Genetics & Genomics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid (IIS-FJD, UAM), Centre for Biomedical Network Research on Rare Diseases (CIBERER), Madrid, Spain
| | - Esther Lantero
- Department of Genetics & Genomics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid (IIS-FJD, UAM), Centre for Biomedical Network Research on Rare Diseases (CIBERER), Madrid, Spain
| | - Fiona Blanco-Kelly
- Department of Genetics & Genomics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid (IIS-FJD, UAM), Centre for Biomedical Network Research on Rare Diseases (CIBERER), Madrid, Spain
| | - Almudena Avila-Fernandez
- Department of Genetics & Genomics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid (IIS-FJD, UAM), Centre for Biomedical Network Research on Rare Diseases (CIBERER), Madrid, Spain
| | - Inmaculada Martin Merida
- Department of Genetics & Genomics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid (IIS-FJD, UAM), Centre for Biomedical Network Research on Rare Diseases (CIBERER), Madrid, Spain
| | - Marta Del Pozo-Valero
- Department of Genetics & Genomics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid (IIS-FJD, UAM), Centre for Biomedical Network Research on Rare Diseases (CIBERER), Madrid, Spain
| | - Irene Perea-Romero
- Department of Genetics & Genomics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid (IIS-FJD, UAM), Centre for Biomedical Network Research on Rare Diseases (CIBERER), Madrid, Spain
| | - Olga Zurita
- Department of Genetics & Genomics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid (IIS-FJD, UAM), Centre for Biomedical Network Research on Rare Diseases (CIBERER), Madrid, Spain
| | - Belén Jiménez-Rolando
- Department of Ophthalmology, Fundación Jiménez Díaz University Hospital (FJD), Madrid, Spain
| | - Saoud Tahsin Swafiri
- Department of Genetics & Genomics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid (IIS-FJD, UAM), Centre for Biomedical Network Research on Rare Diseases (CIBERER), Madrid, Spain
| | - Rosa Riveiro-Alvarez
- Department of Genetics & Genomics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid (IIS-FJD, UAM), Centre for Biomedical Network Research on Rare Diseases (CIBERER), Madrid, Spain
| | - María José Trujillo-Tiebas
- Department of Genetics & Genomics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid (IIS-FJD, UAM), Centre for Biomedical Network Research on Rare Diseases (CIBERER), Madrid, Spain
| | - Ester Carreño Salas
- Department of Ophthalmology, Fundación Jiménez Díaz University Hospital (FJD), Madrid, Spain
| | - Blanca García-Sandoval
- Department of Ophthalmology, Fundación Jiménez Díaz University Hospital (FJD), Madrid, Spain
| | - Marta Corton
- Department of Genetics & Genomics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid (IIS-FJD, UAM), Centre for Biomedical Network Research on Rare Diseases (CIBERER), Madrid, Spain
| | - Carmen Ayuso
- Department of Genetics & Genomics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid (IIS-FJD, UAM), Centre for Biomedical Network Research on Rare Diseases (CIBERER), Madrid, Spain.
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9
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Blum E, Zhang J, Zaluski J, Einstein DE, Korshin EE, Kubas A, Gruzman A, Tochtrop GP, Kiser PD, Palczewski K. Rational Alteration of Pharmacokinetics of Chiral Fluorinated and Deuterated Derivatives of Emixustat for Retinal Therapy. J Med Chem 2021; 64:8287-8302. [PMID: 34081480 DOI: 10.1021/acs.jmedchem.1c00279] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Recycling of all-trans-retinal to 11-cis-retinal through the visual cycle is a fundamental metabolic pathway in the eye. A potent retinoid isomerase (RPE65) inhibitor, (R)-emixustat, has been developed and tested in several clinical trials; however, it has not received regulatory approval for use in any specific retinopathy. Rapid clearance of this drug presents challenges to maintaining concentrations in eyes within a therapeutic window. To address this pharmacokinetic inadequacy, we rationally designed and synthesized a series of emixustat derivatives with strategically placed fluorine and deuterium atoms to slow down the key metabolic transformations known for emixustat. Crystal structures and quantum chemical analysis of RPE65 in complex with the most potent emixustat derivatives revealed the structural and electronic bases for how fluoro substituents can be favorably accommodated within the active site pocket of RPE65. We found a close (∼3.0 Å) F-π interaction that is predicted to contribute ∼2.4 kcal/mol to the overall binding energy.
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Affiliation(s)
- Eliav Blum
- Department of Chemistry, Faculty of Exact Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Jianye Zhang
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, California 92697, United States
| | - Jordan Zaluski
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - David E Einstein
- Department of Physiology and Biophysics, University of California, Irvine, California 92697, United States.,Research Service, VA Long Beach Healthcare System, Long Beach, California 90822, United States
| | - Edward E Korshin
- Department of Chemistry, Faculty of Exact Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Adam Kubas
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, Warsaw 01-224, Poland
| | - Arie Gruzman
- Department of Chemistry, Faculty of Exact Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Gregory P Tochtrop
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - Philip D Kiser
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, California 92697, United States.,Department of Physiology and Biophysics, University of California, Irvine, California 92697, United States.,Research Service, VA Long Beach Healthcare System, Long Beach, California 90822, United States
| | - Krzysztof Palczewski
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, California 92697, United States.,Department of Physiology and Biophysics, University of California, Irvine, California 92697, United States.,Department of Chemistry, University of California, Irvine, California 92697, United States
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10
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Kuatsjah E, Chan ACK, Katahira R, Haugen SJ, Beckham GT, Murphy MEP, Eltis LD. Structural and functional analysis of lignostilbene dioxygenases from Sphingobium sp. SYK-6. J Biol Chem 2021; 296:100758. [PMID: 33965373 PMCID: PMC8191317 DOI: 10.1016/j.jbc.2021.100758] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 04/28/2021] [Accepted: 05/03/2021] [Indexed: 11/27/2022] Open
Abstract
Lignostilbene-α,β-dioxygenases (LSDs) are iron-dependent oxygenases involved in the catabolism of lignin-derived stilbenes. Sphingobium sp. SYK-6 contains eight LSD homologs with undetermined physiological roles. To investigate which homologs are involved in the catabolism of dehydrodiconiferyl alcohol (DCA), derived from β-5 linked lignin subunits, we heterologously produced the enzymes and screened their activities in lysates. The seven soluble enzymes all cleaved lignostilbene, but only LSD2, LSD3, and LSD4 exhibited high specific activity for 3-(4-hydroxy-3-(4-hydroxy-3-methoxystyryl)-5-methoxyphenyl) acrylate (DCA-S) relative to lignostilbene. LSD4 catalyzed the cleavage of DCA-S to 5-formylferulate and vanillin and cleaved lignostilbene and DCA-S (∼106 M−1 s−1) with tenfold greater specificity than pterostilbene and resveratrol. X-ray crystal structures of native LSD4 and the catalytically inactive cobalt-substituted Co-LSD4 at 1.45 Å resolution revealed the same fold, metal ion coordination, and edge-to-edge dimeric structure as observed in related enzymes. Key catalytic residues, Phe-59, Tyr-101, and Lys-134, were also conserved. Structures of Co-LSD4·vanillin, Co-LSD4·lignostilbene, and Co-LSD4·DCA-S complexes revealed that Ser-283 forms a hydrogen bond with the hydroxyl group of the ferulyl portion of DCA-S. This residue is conserved in LSD2 and LSD4 but is alanine in LSD3. Substitution of Ser-283 with Ala minimally affected the specificity of LSD4 for either lignostilbene or DCA-S. By contrast, substitution with phenylalanine, as occurs in LSD5 and LSD6, reduced the specificity of the enzyme for both substrates by an order of magnitude. This study expands our understanding of an LSD critical to DCA catabolism as well as the physiological roles of other LSDs and their determinants of substrate specificity.
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Affiliation(s)
- Eugene Kuatsjah
- Department of Microbiology and Immunology, Life Sciences Institute, The University of British Columbia, Vancouver, Canada; Renewable Resources and Enabling Sciences Center, National Renewable Energy Laboratory, Golden, Colorado, USA; Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge Tennessee, USA
| | - Anson C K Chan
- Department of Microbiology and Immunology, Life Sciences Institute, The University of British Columbia, Vancouver, Canada
| | - Rui Katahira
- Renewable Resources and Enabling Sciences Center, National Renewable Energy Laboratory, Golden, Colorado, USA
| | - Stefan J Haugen
- Renewable Resources and Enabling Sciences Center, National Renewable Energy Laboratory, Golden, Colorado, USA
| | - Gregg T Beckham
- Renewable Resources and Enabling Sciences Center, National Renewable Energy Laboratory, Golden, Colorado, USA; Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge Tennessee, USA
| | - Michael E P Murphy
- Department of Microbiology and Immunology, Life Sciences Institute, The University of British Columbia, Vancouver, Canada; BioProducts Institute, The University of British Columbia, Vancouver, Canada
| | - Lindsay D Eltis
- Department of Microbiology and Immunology, Life Sciences Institute, The University of British Columbia, Vancouver, Canada; BioProducts Institute, The University of British Columbia, Vancouver, Canada.
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11
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Gao J, Yang S, Tang K, Li G, Gao X, Liu B, Wang S, Feng X. GmCCD4 controls carotenoid content in soybeans. PLANT BIOTECHNOLOGY JOURNAL 2021; 19:801-813. [PMID: 33131209 PMCID: PMC8051601 DOI: 10.1111/pbi.13506] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 10/06/2020] [Accepted: 10/26/2020] [Indexed: 05/23/2023]
Abstract
To better understand the mechanisms regulating plant carotenoid metabolism in staple crop, we report the map-based cloning and functional characterization of the Glycine max carotenoid cleavage dioxygenase 4 (GmCCD4) gene, which encodes a carotenoid cleavage dioxygenase enzyme involved in metabolizing carotenoids into volatile β-ionone. Loss of GmCCD4 protein function in four Glycine max increased carotenoid content (gmicc) mutants resulted in yellow flowers due to excessive accumulation of carotenoids in flower petals. The carotenoid contents also increase three times in gmicc1 seeds. A genome-wide association study indicated that the GmCCD4 locus was one major locus associated with carotenoid content in natural population. Further analysis indicated that the haplotype-1 of GmCCD4 gene was positively associated with higher carotenoid levels in soybean cultivars and accumulated more β-carotene in engineered E. coli with ectopic expression of different GmCCD4 haplotypes. These observations uncovered that GmCCD4 was a negative regulator of carotenoid content in soybean, and its various haplotypes provide useful resources for future soybean breeding practice.
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Affiliation(s)
- Jinshan Gao
- Key Laboratory of Soybean Molecular Design BreedingNortheast Institute of Geography and AgroecologyChinese Academy of SciencesChangchunChina
| | - Suxin Yang
- Key Laboratory of Soybean Molecular Design BreedingNortheast Institute of Geography and AgroecologyChinese Academy of SciencesChangchunChina
| | - Kuanqiang Tang
- Key Laboratory of Soybean Molecular Design BreedingNortheast Institute of Geography and AgroecologyChinese Academy of SciencesChangchunChina
| | - Guang Li
- Key Laboratory of Soybean Molecular Design BreedingNortheast Institute of Geography and AgroecologyChinese Academy of SciencesChangchunChina
| | - Xiang Gao
- Key Laboratory of Molecular Epigenetics of Ministry of Education (MOE)Northeast Normal UniversityChangchunChina
| | - Bao Liu
- Key Laboratory of Molecular Epigenetics of Ministry of Education (MOE)Northeast Normal UniversityChangchunChina
| | - Shaodong Wang
- Key Laboratory of Soybean Biology of Education MinistryNortheast Agricultural UniversityHarbinChina
| | - Xianzhong Feng
- Key Laboratory of Soybean Molecular Design BreedingNortheast Institute of Geography and AgroecologyChinese Academy of SciencesChangchunChina
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12
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Choi EH, Daruwalla A, Suh S, Leinonen H, Palczewski K. Retinoids in the visual cycle: role of the retinal G protein-coupled receptor. J Lipid Res 2021; 62:100040. [PMID: 32493732 PMCID: PMC7910522 DOI: 10.1194/jlr.tr120000850] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 05/20/2020] [Indexed: 12/13/2022] Open
Abstract
Driven by the energy of a photon, the visual pigments in rod and cone photoreceptor cells isomerize 11-cis-retinal to the all-trans configuration. This photochemical reaction initiates the signal transduction pathway that eventually leads to the transmission of a visual signal to the brain and leaves the opsins insensitive to further light stimulation. For the eye to restore light sensitivity, opsins require recharging with 11-cis-retinal. This trans-cis back conversion is achieved through a series of enzymatic reactions composing the retinoid (visual) cycle. Although it is evident that the classical retinoid cycle is critical for vision, the existence of an adjunct pathway for 11-cis-retinal regeneration has been debated for many years. Retinal pigment epithelium (RPE)-retinal G protein-coupled receptor (RGR) has been identified previously as a mammalian retinaldehyde photoisomerase homologous to retinochrome found in invertebrates. Using pharmacological, genetic, and biochemical approaches, researchers have now established the physiological relevance of the RGR in 11-cis-retinal regeneration. The photoisomerase activity of RGR in the RPE and Müller glia explains how the eye can remain responsive in daylight. In this review, we will focus on retinoid metabolism in the eye and visual chromophore regeneration mediated by RGR.
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Affiliation(s)
- Elliot H Choi
- Department of Ophthalmology, Gavin Herbert Eye Institute, Center for Translational Vision Research, University of California, Irvine, CA, USA; Department of Pharmacology, Case Western Reserve University, Cleveland, OH, USA.
| | - Anahita Daruwalla
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH, USA; Departments of Physiology and Biophysics, and Chemistry, University of California, Irvine, CA, USA
| | - Susie Suh
- Department of Ophthalmology, Gavin Herbert Eye Institute, Center for Translational Vision Research, University of California, Irvine, CA, USA; Department of Pharmacology, Case Western Reserve University, Cleveland, OH, USA
| | - Henri Leinonen
- Department of Ophthalmology, Gavin Herbert Eye Institute, Center for Translational Vision Research, University of California, Irvine, CA, USA
| | - Krzysztof Palczewski
- Department of Ophthalmology, Gavin Herbert Eye Institute, Center for Translational Vision Research, University of California, Irvine, CA, USA; Departments of Physiology and Biophysics, and Chemistry, University of California, Irvine, CA, USA.
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13
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Kiser PD, Palczewski K. Pathways and disease-causing alterations in visual chromophore production for vertebrate vision. J Biol Chem 2021; 296:100072. [PMID: 33187985 PMCID: PMC7948990 DOI: 10.1074/jbc.rev120.014405] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 11/12/2020] [Accepted: 11/13/2020] [Indexed: 12/14/2022] Open
Abstract
All that we view of the world begins with an ultrafast cis to trans photoisomerization of the retinylidene chromophore associated with the visual pigments of rod and cone photoreceptors. The continual responsiveness of these photoreceptors is then sustained by regeneration processes that convert the trans-retinoid back to an 11-cis configuration. Recent biochemical and electrophysiological analyses of the retinal G-protein-coupled receptor (RGR) suggest that it could sustain the responsiveness of photoreceptor cells, particularly cones, even under bright light conditions. Thus, two mechanisms have evolved to accomplish the reisomerization: one involving the well-studied retinoid isomerase (RPE65) and a second photoisomerase reaction mediated by the RGR. Impairments to the pathways that transform all-trans-retinal back to 11-cis-retinal are associated with mild to severe forms of retinal dystrophy. Moreover, with age there also is a decline in the rate of chromophore regeneration. Both pharmacological and genetic approaches are being used to bypass visual cycle defects and consequently mitigate blinding diseases. Rapid progress in the use of genome editing also is paving the way for the treatment of disparate retinal diseases. In this review, we provide an update on visual cycle biochemistry and then discuss visual-cycle-related diseases and emerging therapeutics for these disorders. There is hope that these advances will be helpful in treating more complex diseases of the eye, including age-related macular degeneration (AMD).
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Affiliation(s)
- Philip D Kiser
- The Department of Physiology & Biophysics, University of California, Irvine, California, USA; Research Service, The VA Long Beach Health Care System, Long Beach, California, USA; The Gavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, California, USA.
| | - Krzysztof Palczewski
- The Department of Physiology & Biophysics, University of California, Irvine, California, USA; The Gavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, California, USA; The Department of Chemistry, University of California, Irvine, California, USA.
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14
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Properties and Therapeutic Implications of an Enigmatic D477G RPE65 Variant Associated with Autosomal Dominant Retinitis Pigmentosa. Genes (Basel) 2020; 11:genes11121420. [PMID: 33261050 PMCID: PMC7760593 DOI: 10.3390/genes11121420] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 11/24/2020] [Accepted: 11/24/2020] [Indexed: 12/22/2022] Open
Abstract
RPE65 isomerase, expressed in the retinal pigmented epithelium (RPE), is an enzymatic component of the retinoid cycle, converting all-trans retinyl ester into 11-cis retinol, and it is essential for vision, because it replenishes the photon capturing 11-cis retinal. To date, almost 200 loss-of-function mutations have been identified within the RPE65 gene causing inherited retinal dystrophies, most notably Leber congenital amaurosis (LCA) and autosomal recessive retinitis pigmentosa (arRP), which are both severe and early onset disease entities. We previously reported a mutation, D477G, co-segregating with the disease in a late-onset form of autosomal dominant RP (adRP) with choroidal involvement; uniquely, it is the only RPE65 variant to be described with a dominant component. Families or individuals with this variant have been encountered in five countries, and a number of subsequent studies have been reported in which the molecular biological and physiological properties of the variant have been studied in further detail, including observations of possible novel functions in addition to reduced RPE65 enzymatic activity. With regard to the latter, a human phase 1b proof-of-concept study has recently been reported in which aspects of remaining vision were improved for up to one year in four of five patients with advanced disease receiving a single one-week oral dose of 9-cis retinaldehyde, which is the first report showing efficacy and safety of an oral therapy for a dominant form of RP. Here, we review data accrued from published studies investigating molecular mechanisms of this unique variant and include hitherto unpublished material on the clinical spectrum of disease encountered in patients with the D477G variant, which, in many cases bears striking similarities to choroideremia.
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15
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Poliakov E, Uppal S, Rogozin IB, Gentleman S, Redmond TM. Evolutionary aspects and enzymology of metazoan carotenoid cleavage oxygenases. Biochim Biophys Acta Mol Cell Biol Lipids 2020; 1865:158665. [PMID: 32061750 PMCID: PMC7423639 DOI: 10.1016/j.bbalip.2020.158665] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 01/25/2020] [Accepted: 02/05/2020] [Indexed: 12/18/2022]
Abstract
The carotenoids are terpenoid fat-soluble pigments produced by plants, algae, and several bacteria and fungi. They are ubiquitous components of animal diets. Carotenoid cleavage oxygenase (CCO) superfamily members are involved in carotenoid metabolism and are present in all kingdoms of life. Throughout the animal kingdom, carotenoid oxygenases are widely distributed and they are completely absent only in two unicellular organisms, Monosiga and Leishmania. Mammals have three paralogs 15,15'-β-carotene oxygenase (BCO1), 9',10'-β-carotene oxygenase (BCO2) and RPE65. The first two enzymes are classical carotenoid oxygenases: they cleave carbon‑carbon double bonds and incorporate two atoms of oxygen in the substrate at the site of cleavage. The third, RPE65, is an unusual family member, it is the retinoid isomerohydrolase in the visual cycle that converts all-trans-retinyl ester into 11-cis-retinol. Here we discuss evolutionary aspects of the carotenoid cleavage oxygenase superfamily and their enzymology to deduce what insight we can obtain from their evolutionary conservation.
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Affiliation(s)
- Eugenia Poliakov
- Laboratory of Retinal Cell & Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Sheetal Uppal
- Laboratory of Retinal Cell & Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Igor B Rogozin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
| | - Susan Gentleman
- Laboratory of Retinal Cell & Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - T Michael Redmond
- Laboratory of Retinal Cell & Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
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16
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Abstract
The visual phototransduction cascade begins with a cis-trans photoisomerization of a retinylidene chromophore associated with the visual pigments of rod and cone photoreceptors. Visual opsins release their all-trans-retinal chromophore following photoactivation, which necessitates the existence of pathways that produce 11-cis-retinal for continued formation of visual pigments and sustained vision. Proteins in the retinal pigment epithelium (RPE), a cell layer adjacent to the photoreceptor outer segments, form the well-established "dark" regeneration pathway known as the classical visual cycle. This pathway is sufficient to maintain continuous rod function and support cone photoreceptors as well although its throughput has to be augmented by additional mechanism(s) to maintain pigment levels in the face of high rates of photon capture. Recent studies indicate that the classical visual cycle works together with light-dependent processes in both the RPE and neural retina to ensure adequate 11-cis-retinal production under natural illuminances that can span ten orders of magnitude. Further elucidation of the interplay between these complementary systems is fundamental to understanding how cone-mediated vision is sustained in vivo. Here, we describe recent advances in understanding how 11-cis-retinal is synthesized via light-dependent mechanisms.
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17
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Structural basis for carotenoid cleavage by an archaeal carotenoid dioxygenase. Proc Natl Acad Sci U S A 2020; 117:19914-19925. [PMID: 32747548 DOI: 10.1073/pnas.2004116117] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Apocarotenoids are important signaling molecules generated from carotenoids through the action of carotenoid cleavage dioxygenases (CCDs). These enzymes have a remarkable ability to cleave carotenoids at specific alkene bonds while leaving chemically similar sites within the polyene intact. Although several bacterial and eukaryotic CCDs have been characterized, the long-standing goal of experimentally visualizing a CCD-carotenoid complex at high resolution to explain this exquisite regioselectivity remains unfulfilled. CCD genes are also present in some archaeal genomes, but the encoded enzymes remain uninvestigated. Here, we address this knowledge gap through analysis of a metazoan-like archaeal CCD from Candidatus Nitrosotalea devanaterra (NdCCD). NdCCD was active toward β-apocarotenoids but did not cleave bicyclic carotenoids. It exhibited an unusual regiospecificity, cleaving apocarotenoids solely at the C14'-C13' alkene bond to produce β-apo-14'-carotenals. The structure of NdCCD revealed a tapered active site cavity markedly different from the broad active site observed for the retinal-forming Synechocystis apocarotenoid oxygenase (SynACO) but similar to the vertebrate retinoid isomerase RPE65. The structure of NdCCD in complex with its apocarotenoid product demonstrated that the site of cleavage is defined by interactions along the substrate binding cleft as well as selective stabilization of reaction intermediates at the scissile alkene. These data on the molecular basis of CCD catalysis shed light on the origins of the varied catalytic activities found in metazoan CCDs, opening the possibility of modifying their activity through rational chemical or genetic approaches.
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18
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Structural dynamics in the C terminal domain homolog of orange carotenoid Protein reveals residues critical for carotenoid uptake. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2020; 1861:148214. [DOI: 10.1016/j.bbabio.2020.148214] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Revised: 03/19/2020] [Accepted: 04/27/2020] [Indexed: 01/01/2023]
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19
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von Lintig J, Moon J, Babino D. Molecular components affecting ocular carotenoid and retinoid homeostasis. Prog Retin Eye Res 2020; 80:100864. [PMID: 32339666 DOI: 10.1016/j.preteyeres.2020.100864] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 04/13/2020] [Accepted: 04/17/2020] [Indexed: 12/15/2022]
Abstract
The photochemistry of vision employs opsins and geometric isomerization of their covalently bound retinylidine chromophores. In different animal classes, these light receptors associate with distinct G proteins that either hyperpolarize or depolarize photoreceptor membranes. Vertebrates also use the acidic form of chromophore, retinoic acid, as the ligand of nuclear hormone receptors that orchestrate eye development. To establish and sustain these processes, animals must acquire carotenoids from the diet, transport them, and metabolize them to chromophore and retinoic acid. The understanding of carotenoid metabolism, however, lagged behind our knowledge about the biology of their receptor molecules. In the past decades, much progress has been made in identifying the genes encoding proteins that mediate the transport and enzymatic transformations of carotenoids and their retinoid metabolites. Comparative analysis in different animal classes revealed how evolutionary tinkering with a limited number of genes evolved different biochemical strategies to supply photoreceptors with chromophore. Mutations in these genes impair carotenoid metabolism and induce various ocular pathologies. This review summarizes this advancement and introduces the involved proteins, including the homeostatic regulation of their activities.
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Affiliation(s)
- Johannes von Lintig
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA.
| | - Jean Moon
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Darwin Babino
- Department of Ophthalmology, School of Medicine, University of Washington, Seattle, WA, USA
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20
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Daruwalla A, Kiser PD. Structural and mechanistic aspects of carotenoid cleavage dioxygenases (CCDs). Biochim Biophys Acta Mol Cell Biol Lipids 2019; 1865:158590. [PMID: 31874225 DOI: 10.1016/j.bbalip.2019.158590] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 12/10/2019] [Accepted: 12/11/2019] [Indexed: 02/03/2023]
Abstract
Carotenoid cleavage dioxygenases (CCDs) comprise a superfamily of mononuclear non-heme iron proteins that catalyze the oxygenolytic fission of alkene bonds in carotenoids to generate apocarotenoid products. Some of these enzymes exhibit additional activities such as carbon skeleton rearrangement and trans-cis isomerization. The group also includes a subfamily of enzymes that split the interphenyl alkene bond in molecules such as resveratrol and lignostilbene. CCDs are involved in numerous biological processes ranging from production of light-sensing chromophores to degradation of lignin derivatives in pulping waste sludge. These enzymes exhibit unique features that distinguish them from other families of non-heme iron enzymes. The distinctive properties and biological importance of CCDs have stimulated interest in their modes of catalysis. Recent structural, spectroscopic, and computational studies have helped clarify mechanistic aspects of CCD catalysis. Here, we review these findings emphasizing common and unique properties of CCDs that enable their variable substrate specificity and regioselectivity. This article is part of a Special Issue entitled Carotenoids recent advances in cell and molecular biology edited by Johannes von Lintig and Loredana Quadro.
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Affiliation(s)
- Anahita Daruwalla
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH 44106, United States of America; Department of Physiology & Biophysics, University of California, Irvine, CA 92697, United States of America
| | - Philip D Kiser
- Department of Physiology & Biophysics, University of California, Irvine, CA 92697, United States of America; Research Service, VA Long Beach Healthcare System, Long Beach, CA 90822, United States of America.
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21
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Uppal S, Liu T, Poliakov E, Gentleman S, Redmond TM. The dual roles of RPE65 S-palmitoylation in membrane association and visual cycle function. Sci Rep 2019; 9:5218. [PMID: 30914787 PMCID: PMC6435699 DOI: 10.1038/s41598-019-41501-w] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Accepted: 03/07/2019] [Indexed: 12/31/2022] Open
Abstract
Association with the endoplasmic reticulum (ER) membrane is a critical requirement for the catalytic function of RPE65. Several studies have investigated the nature of the RPE65-membrane interaction; however, complete understanding of its mode of membrane binding is still lacking. Previous biochemical studies suggest the membrane interaction can be partly attributed to S-palmitoylation, but the existence of RPE65 palmitoylation remains a matter of debate. Here, we re-examined RPE65 palmitoylation, and its functional consequence in the visual cycle. We clearly demonstrate that RPE65 is post-translationally modified by a palmitoyl moiety, but this is not universal (about 25% of RPE65). By extensive mutational studies we mapped the S-palmitoylation sites to residues C112 and C146. Inhibition of palmitoylation using 2-bromopalmitate and 2-fluoropalmitate completely abolish its membrane association. Furthermore, palmitoylation-deficient C112 mutants are significantly impeded in membrane association. Finally, we show that RPE65 palmitoylation level is highly regulated by lecithin:retinol acyltransferase (LRAT) enzyme. In the presence of all-trans retinol, LRAT substrate, there is a significant decrease in the level of palmitoylation of RPE65. In conclusion, our findings suggest that RPE65 is indeed a dynamically-regulated palmitoylated protein and that palmitoylation is necessary for regulating its membrane binding, and to perform its normal visual cycle function.
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Affiliation(s)
- Sheetal Uppal
- Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, MD, 20892, United States
| | - Tingting Liu
- Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, MD, 20892, United States.,Department of Transfusion, The Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, 210008, P.R. China
| | - Eugenia Poliakov
- Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, MD, 20892, United States
| | - Susan Gentleman
- Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, MD, 20892, United States
| | - T Michael Redmond
- Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, MD, 20892, United States.
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22
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Choi EH, Suh S, Sander CL, Hernandez CJO, Bulman ER, Khadka N, Dong Z, Shi W, Palczewski K, Kiser PD. Insights into the pathogenesis of dominant retinitis pigmentosa associated with a D477G mutation in RPE65. Hum Mol Genet 2019; 27:2225-2243. [PMID: 29659842 DOI: 10.1093/hmg/ddy128] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Accepted: 04/06/2018] [Indexed: 12/31/2022] Open
Abstract
RPE65 is the essential trans-cis isomerase of the classical retinoid (visual) cycle. Mutations in RPE65 give rise to severe retinal dystrophies, most of which are associated with loss of protein function and recessive inheritance. The only known exception is a c.1430G>A (D477G) mutation that gives rise to dominant retinitis pigmentosa with delayed onset and choroidal and macular involvement. Position 477 is distant from functionally critical regions of RPE65. Hence, the mechanism of D477G pathogenicity remains unclear, although protein misfolding and aggregation mechanisms have been suggested. We characterized a D477G knock-in mouse model which exhibited mild age-dependent changes in retinal structure and function. Immunoblot analysis of protein extracts from the eyes of these knock-in mice demonstrated the presence of ubiquitinated RPE65 and reduced RPE65 expression. We observed an accumulation of retinyl esters in the knock-in mice as well as a delay in rhodopsin regeneration kinetics and diminished electroretinography responses, indicative of RPE65 functional impairment induced by the D477G mutation in vivo. However, a cell line expressing D477G RPE65 revealed protein expression levels, cellular localization and retinoid isomerase activity comparable to cells expressing wild-type protein. Structural analysis of an RPE65 chimera suggested that the D477G mutation does not perturb protein folding or tertiary structure. Instead, the mutation generates an aggregation-prone surface that could induce cellular toxicity through abnormal complex formation as suggested by crystal packing analysis. These results indicate that a toxic gain-of-function induced by the D477G RPE65 substitution may play a role in the pathogenesis of this form of dominant retinitis pigmentosa.
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Affiliation(s)
- Elliot H Choi
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Susie Suh
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Christopher L Sander
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Christian J Ortiz Hernandez
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA.,University of Puerto Rico at Humacao, Humacao, PR, USA
| | - Elizabeth R Bulman
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA.,Research Service, Louis Stokes Cleveland VA Medical Center, Cleveland, OH 44106, USA
| | - Nimesh Khadka
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Zhiqian Dong
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA.,Polgenix Inc., Cleveland, OH 44106, USA
| | - Wuxian Shi
- National Synchrotron Light Source-II, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Krzysztof Palczewski
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA.,Cleveland Center for Membrane and Structural Biology, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Philip D Kiser
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA.,Research Service, Louis Stokes Cleveland VA Medical Center, Cleveland, OH 44106, USA.,Cleveland Center for Membrane and Structural Biology, Case Western Reserve University, Cleveland, OH 44106, USA
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23
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Allen KN, Entova S, Ray LC, Imperiali B. Monotopic Membrane Proteins Join the Fold. Trends Biochem Sci 2019; 44:7-20. [PMID: 30337134 PMCID: PMC6309722 DOI: 10.1016/j.tibs.2018.09.013] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Revised: 09/18/2018] [Accepted: 09/19/2018] [Indexed: 12/22/2022]
Abstract
Monotopic membrane proteins, classified by topology, are proteins that embed into a single face of the membrane. These proteins are generally underrepresented in the Protein Data Bank (PDB), but the past decade of research has revealed new examples that allow the description of generalizable features. This Opinion article summarizes shared characteristics including oligomerization states, modes of membrane association, mechanisms of interaction with hydrophobic or amphiphilic substrates, and homology to soluble folds. We also discuss how associations of monotopic enzymes in pathways can be used to promote substrate specificity and product composition. These examples highlight the challenges in structure determination specific to this class of proteins, but also the promise of new understanding from future study of these proteins that reside at the interface.
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Affiliation(s)
- Karen N Allen
- Department of Chemistry, Boston University, Boston, MA 02215, USA; Program in Biomolecular Pharmacology, Boston University School of Medicine, Boston, MA 02118, USA.
| | - Sonya Entova
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Leah C Ray
- Program in Biomolecular Pharmacology, Boston University School of Medicine, Boston, MA 02118, USA
| | - Barbara Imperiali
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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24
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Structural biology of 11- cis-retinaldehyde production in the classical visual cycle. Biochem J 2018; 475:3171-3188. [PMID: 30352831 DOI: 10.1042/bcj20180193] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 09/20/2018] [Accepted: 09/26/2018] [Indexed: 12/21/2022]
Abstract
The vitamin A derivative 11-cis-retinaldehyde plays a pivotal role in vertebrate vision by serving as the chromophore of rod and cone visual pigments. In the initial step of vision, a photon is absorbed by this chromophore resulting in its isomerization to an all-trans state and consequent activation of the visual pigment and phototransduction cascade. Spent chromophore is released from the pigments through hydrolysis. Subsequent photon detection requires the delivery of regenerated 11-cis-retinaldehyde to the visual pigment. This trans-cis conversion is achieved through a process known as the visual cycle. In this review, we will discuss the enzymes, binding proteins and transporters that enable the visual pigment renewal process with a focus on advances made during the past decade in our understanding of their structural biology.
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Sui X, Farquhar ER, Hill HE, von Lintig J, Shi W, Kiser PD. Preparation and characterization of metal-substituted carotenoid cleavage oxygenases. J Biol Inorg Chem 2018; 23:887-901. [PMID: 29946976 PMCID: PMC6060882 DOI: 10.1007/s00775-018-1586-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Accepted: 06/20/2018] [Indexed: 11/26/2022]
Abstract
Carotenoid cleavage oxygenases (CCO) are non-heme iron enzymes that catalyze oxidative cleavage of alkene bonds in carotenoid and stilbenoid substrates. Previously, we showed that the iron cofactor of CAO1, a resveratrol-cleaving member of this family, can be substituted with cobalt to yield a catalytically inert enzyme useful for trapping active site-bound stilbenoid substrates for structural characterization. Metal substitution may provide a general method for identifying the natural substrates for CCOs in addition to facilitating structural and biophysical characterization of CCO-carotenoid complexes under normal aerobic conditions. Here, we demonstrate the general applicability of cobalt substitution in a prototypical carotenoid cleaving CCO, apocarotenoid oxygenase (ACO) from Synechocystis. Among the non-native divalent metals investigated, cobalt was uniquely able to stably occupy the ACO metal binding site and inhibit catalysis. Analysis by X-ray crystallography and X-ray absorption spectroscopy demonstrate that the Co(II) forms of both ACO and CAO1 exhibit a close structural correspondence to the native Fe(II) enzyme forms. Hence, cobalt substitution is an effective strategy for generating catalytically inert but structurally intact forms of CCOs.
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Affiliation(s)
- Xuewu Sui
- Department of Pharmacology, School of Medicine, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH, 44106, USA
- Department of Genetics and Complex Diseases, Harvard T.H. Chan School of Public Health, Boston, MA, 02115, USA
| | - Erik R Farquhar
- National Synchrotron Light Source-II, Brookhaven National Laboratory, Upton, NY, 11973, USA
- Center for Proteomics and Bioinformatics, Center for Synchrotron Biosciences, School of Medicine, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH, 44106-4988, USA
| | - Hannah E Hill
- Department of Pharmacology, School of Medicine, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH, 44106, USA
| | - Johannes von Lintig
- Department of Pharmacology, School of Medicine, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH, 44106, USA
| | - Wuxian Shi
- National Synchrotron Light Source-II, Brookhaven National Laboratory, Upton, NY, 11973, USA
- Center for Proteomics and Bioinformatics, Center for Synchrotron Biosciences, School of Medicine, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH, 44106-4988, USA
| | - Philip D Kiser
- Department of Pharmacology, School of Medicine, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH, 44106, USA.
- Cleveland Center for Membrane and Structural Biology, Case Western Reserve University, 1819 E 101st Street, Cleveland, OH, 44106, USA.
- Research Service, Louis Stokes Cleveland VA Medical Center, 10701 East Boulevard, Cleveland, OH, 44106, USA.
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Ward R, Sundaramurthi H, Di Giacomo V, Kennedy BN. Enhancing Understanding of the Visual Cycle by Applying CRISPR/Cas9 Gene Editing in Zebrafish. Front Cell Dev Biol 2018; 6:37. [PMID: 29696141 PMCID: PMC5904205 DOI: 10.3389/fcell.2018.00037] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Accepted: 03/19/2018] [Indexed: 01/23/2023] Open
Abstract
During the vertebrate visual cycle, all-trans-retinal is exported from photoreceptors to the adjacent RPE or Müller glia wherein 11-cis-retinal is regenerated. The 11-cis chromophore is returned to photoreceptors, forming light-sensitive visual pigments with opsin GPCRs. Dysfunction of this process perturbs phototransduction because functional visual pigment cannot be generated. Mutations in visual cycle genes can result in monogenic inherited forms of blindness. Though key enzymatic processes are well characterized, questions remain as to the physiological role of visual cycle proteins in different retinal cell types, functional domains of these proteins in retinoid biochemistry and in vivo pathogenesis of disease mutations. Significant progress is needed to develop effective and accessible treatments for inherited blindness arising from mutations in visual cycle genes. Here, we review opportunities to apply gene editing technology to two crucial visual cycle components, RPE65 and CRALBP. Expressed exclusively in the human RPE, RPE65 enzymatically converts retinyl esters into 11-cis retinal. CRALBP is an 11-cis-retinal binding protein expressed in human RPE and Muller glia. Loss-of-function mutations in either protein results in autosomal recessive forms of blindness. Modeling these human conditions using RPE65 or CRALBP murine knockout models have enhanced our understanding of their biochemical function, associated disease pathogenesis and development of therapeutics. However, rod-dominated murine retinae provide a challenge to assess cone function. The cone-rich zebrafish model is amenable to cost-effective maintenance of a variety of strains. Interestingly, gene duplication in zebrafish resulted in three Rpe65 and two Cralbp isoforms with differential temporal and spatial expression patterns. Functional investigations of zebrafish Rpe65 and Cralbp were restricted to gene knockdown with morpholino oligonucleotides. However, transient silencing, off-target effects and discrepancies between knockdown and knockout models, highlight a need for more comprehensive alternatives for functional genomics. CRISPR/Cas9 in zebrafish has emerged as a formidable technology enabling targeted gene knockout, knock-in, activation, or silencing to single base-pair resolution. Effective, targeted gene editing by CRISPR/Cas9 in zebrafish enables unprecedented opportunities to create genetic research models. This review will discuss existing knowledge gaps regarding RPE65 and CRALBP. We explore the benefits of CRISPR/Cas9 to establish innovative zebrafish models to enhance knowledge of the visual cycle.
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Affiliation(s)
- Rebecca Ward
- UCD School of Biomolecular & Biomedical Science, UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Husvinee Sundaramurthi
- UCD School of Biomolecular & Biomedical Science, UCD Conway Institute, University College Dublin, Dublin, Ireland
- UCD School of Medicine, University College Dublin, Dublin, Ireland
- Systems Biology Ireland, University College Dublin, Dublin, Ireland
| | | | - Breandán N. Kennedy
- UCD School of Biomolecular & Biomedical Science, UCD Conway Institute, University College Dublin, Dublin, Ireland
- *Correspondence: Breandán N. Kennedy
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Ahrazem O, Diretto G, Argandoña J, Rubio-Moraga Á, Julve JM, Orzáez D, Granell A, Gómez-Gómez L. Evolutionarily distinct carotenoid cleavage dioxygenases are responsible for crocetin production in Buddleja davidii. JOURNAL OF EXPERIMENTAL BOTANY 2017; 68:4663-4677. [PMID: 28981773 DOI: 10.1093/jxb/erx277] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Crocetin, one of the few colored apocarotenoids known in nature, is present in flowers and fruits and has long been used medicinally and as a colorant. Saffron is the main source of crocetin, although a few other plants produce lower amounts of this apocarotenoid. Notably, Buddleja davidii accumulates crocetin in its flowers. Recently, a carotenoid dioxygenase cleavage enzyme, CCD2, has been characterized as responsible for crocetin production in Crocus species. We searched for CCD2 homologues in B. davidii and identified several CCD enzymes from the CCD1 and CCD4 subfamilies. Unexpectedly, two out of the three CCD4 enzymes, namely BdCCD4.1 and BdCCD4.3, showed 7,8;7',8' activity in vitro and in vivo over zeaxanthin. In silico analyses of these enzymes and CCD2 allowed the determination of key residues for this activity. Both BdCCD4 genes are highly expressed during flower development and transcripts levels parallel the accumulation of crocins in the petals. Phylogenetic analysis showed that BdCCD4.2 grouped with almost all the characterized CCD4 enzymes, while BdCCD4.1 and BdCCD4.3 form a new sub-cluster together with CCD4 enzymes from certain Lamiales species. The present study indicates that convergent evolution led to the acquisition of 7,8;7',8' apocarotenoid cleavage activity in two separate CCD enzyme families.
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Affiliation(s)
- Oussama Ahrazem
- Instituto Botánico, Departamento de Ciencia y Tecnología Agroforestal y Genética, Facultad de Farmacia, Universidad de Castilla-La Mancha, Campus Universitario s/n, 02071 Albacete, Spain
- Facultad de Ciencias Ambientales y Bioquímica, Universidad de Castilla-La Mancha, Campus Tecnológico de la Fábrica de Armas, Avda, Carlos III s/n, E-45071 Toledo, Spain
| | - Gianfranco Diretto
- Italian National Agency for New Technologies, Energy, and Sustainable Development, Casaccia Research Centre, 00123 Rome, Italy
| | - Javier Argandoña
- Instituto Botánico, Departamento de Ciencia y Tecnología Agroforestal y Genética, Facultad de Farmacia, Universidad de Castilla-La Mancha, Campus Universitario s/n, 02071 Albacete, Spain
| | - Ángela Rubio-Moraga
- Instituto Botánico, Departamento de Ciencia y Tecnología Agroforestal y Genética, Facultad de Farmacia, Universidad de Castilla-La Mancha, Campus Universitario s/n, 02071 Albacete, Spain
| | - José Manuel Julve
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas, Universidad Politécnica de Valencia, Camino de Vera s/n, 46022 Valencia, Spain
| | - Diego Orzáez
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas, Universidad Politécnica de Valencia, Camino de Vera s/n, 46022 Valencia, Spain
| | - Antonio Granell
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas, Universidad Politécnica de Valencia, Camino de Vera s/n, 46022 Valencia, Spain
| | - Lourdes Gómez-Gómez
- Instituto Botánico, Departamento de Ciencia y Tecnología Agroforestal y Genética, Facultad de Farmacia, Universidad de Castilla-La Mancha, Campus Universitario s/n, 02071 Albacete, Spain
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Pharmacological Amelioration of Cone Survival and Vision in a Mouse Model for Leber Congenital Amaurosis. J Neurosci 2017; 36:5808-19. [PMID: 27225770 DOI: 10.1523/jneurosci.3857-15.2016] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2015] [Accepted: 04/20/2016] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED RPE65, an abundant membrane-associate protein in the retinal pigment epithelium (RPE), is a key retinoid isomerase of the visual cycle necessary for generating 11-cis-retinal that functions not only as a molecular switch for activating cone and rod visual pigments in response to light stimulation, but also as a chaperone for normal trafficking of cone opsins to the outer segments. Many mutations in RPE65 are associated with Leber congenital amaurosis (LCA). A R91W substitution, the most frequent LCA-associated mutation, results in a severe decrease in protein level and enzymatic activity of RPE65, causing cone opsin mislocalization and early cone degeneration in the mutation knock-in mouse model of LCA. Here we show that R91W RPE65 undergoes ubiquitination-dependent proteasomal degradation in the knock-in mouse RPE due to misfolding. The 26S proteasome non-ATPase regulatory subunit 13 mediated degradation specifically of misfolded R91W RPE65. The mutation disrupted membrane-association and colocalization of RPE65 with lecithin:retinol acyltransferase (LRAT) that provides the hydrophobic substrate for RPE65. Systemic administration of sodium 4-phenylbutyrate (PBA), a chemical chaperone, increased protein stability, enzymatic activity, membrane-association, and colocalization of R91W RPE65 with LRAT. This rescue effect increased synthesis of 11-cis-retinal and 9-cis-retinal, a functional iso-chromophore of the visual pigments, led to alleviation of S-opsin mislocalization and cone degeneration in the knock-in mice. Importantly, PBA-treatment also improved cone-mediated vision in the mutant mice. These results indicate that PBA, a U.S. Food and Drug Administration-approved safe oral medication, may provide a noninvasive therapeutic intervention that delays daylight vision loss in patients with RPE65 mutations. SIGNIFICANCE STATEMENT LCA is a severe early onset retinal dystrophy. Recent clinical trials of gene therapy have implicated the need of an alternative or combination therapy to improve cone survival and function in patients with LCA caused by RPE65 mutations. Using a mouse model carrying the most frequent LCA-associated mutation (R91W), we found that the mutant RPE65 underwent ubiquitination-dependent proteasomal degradation due to misfolding. Treatment of the mice with a chemical chaperone partially corrected stability, enzymatic activity, and subcellular localization of R91W RPE65, which was also accompanied by improvement of cone survival and vision. These findings identify an in vivo molecular pathogenic mechanism for R91W mutation and provide a feasible pharmacological approach that can delay vision loss in patients with RPE65 mutations.
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Sui X, Weitz AC, Farquhar ER, Badiee M, Banerjee S, von Lintig J, Tochtrop GP, Palczewski K, Hendrich MP, Kiser PD. Structure and Spectroscopy of Alkene-Cleaving Dioxygenases Containing an Atypically Coordinated Non-Heme Iron Center. Biochemistry 2017; 56:2836-2852. [PMID: 28493664 DOI: 10.1021/acs.biochem.7b00251] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Carotenoid cleavage oxygenases (CCOs) are non-heme iron enzymes that catalyze scission of alkene groups in carotenoids and stilbenoids to form biologically important products. CCOs possess a rare four-His iron center whose resting-state structure and interaction with substrates are incompletely understood. Here, we address this knowledge gap through a comprehensive structural and spectroscopic study of three phyletically diverse CCOs. The crystal structure of a fungal stilbenoid-cleaving CCO, CAO1, reveals strong similarity between its iron center and those of carotenoid-cleaving CCOs, but with a markedly different substrate-binding cleft. These enzymes all possess a five-coordinate high-spin Fe(II) center with resting-state Fe-His bond lengths of ∼2.15 Å. This ligand set generates an iron environment more electropositive than those of other non-heme iron dioxygenases as observed by Mössbauer isomer shifts. Dioxygen (O2) does not coordinate iron in the absence of substrate. Substrates bind away (∼4.7 Å) from the iron and have little impact on its electronic structure, thus excluding coordination-triggered O2 binding. However, substrate binding does perturb the spectral properties of CCO Fe-NO derivatives, indicating proximate organic substrate and O2-binding sites, which might influence Fe-O2 interactions. Together, these data provide a robust description of the CCO iron center and its interactions with substrates and substrate mimetics that illuminates commonalities as well as subtle and profound structural differences within the CCO family.
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Affiliation(s)
- Xuewu Sui
- Department of Pharmacology, School of Medicine, Case Western Reserve University , 10900 Euclid Avenue, Cleveland, Ohio 44106, United States
| | - Andrew C Weitz
- Department of Chemistry, Carnegie Mellon University , 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
| | - Erik R Farquhar
- National Synchrotron Light Source-II, Brookhaven National Laboratory , Upton, New York 11973, United States.,Center for Proteomics and Bioinformatics, Center for Synchrotron Biosciences, School of Medicine, Case Western Reserve University , 10900 Euclid Avenue, Cleveland, Ohio 44106-4988, United States
| | - Mohsen Badiee
- Department of Chemistry, Case Western Reserve University , 2080 Adelbert Road, Cleveland, Ohio 44106, United States
| | - Surajit Banerjee
- Department of Chemistry and Chemical Biology, Cornell University , Ithaca, New York 14850, United States.,Northeastern Collaborative Access Team, Argonne National Laboratory , Argonne, Illinois 60439, United States
| | - Johannes von Lintig
- Department of Pharmacology, School of Medicine, Case Western Reserve University , 10900 Euclid Avenue, Cleveland, Ohio 44106, United States
| | - Gregory P Tochtrop
- Department of Chemistry, Case Western Reserve University , 2080 Adelbert Road, Cleveland, Ohio 44106, United States
| | - Krzysztof Palczewski
- Department of Pharmacology, School of Medicine, Case Western Reserve University , 10900 Euclid Avenue, Cleveland, Ohio 44106, United States.,Cleveland Center for Membrane and Structural Biology, Case Western Reserve University , 1819 East 101st Street, Cleveland, Ohio 44106, United States
| | - Michael P Hendrich
- Department of Chemistry, Carnegie Mellon University , 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
| | - Philip D Kiser
- Department of Pharmacology, School of Medicine, Case Western Reserve University , 10900 Euclid Avenue, Cleveland, Ohio 44106, United States.,Research Service, Louis Stokes Cleveland VA Medical Center , 10701 East Boulevard, Cleveland, Ohio 44106, United States
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30
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Abstract
Recent progress in molecular understanding of the retinoid cycle in mammalian retina stems from painstaking biochemical reconstitution studies supported by natural or engineered animal models with known genetic lesions and studies of humans with specific genetic blinding diseases. Structural and membrane biology have been used to detect critical retinal enzymes and proteins and their substrates and ligands, placing them in a cellular context. These studies have been supplemented by analytical chemistry methods that have identified small molecules by their spectral characteristics, often in conjunction with the evaluation of models of animal retinal disease. It is from this background that rational therapeutic interventions to correct genetic defects or environmental insults are identified. Thus, most presently accepted modulators of the retinoid cycle already have demonstrated promising results in animal models of retinal degeneration. These encouraging signs indicate that some human blinding diseases can be alleviated by pharmacological interventions.
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Affiliation(s)
- Philip D Kiser
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106 ; Louis Stokes Cleveland VA Medical Center, Cleveland, Ohio 44106
| | - Krzysztof Palczewski
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106
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31
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Babino D, Golczak M, Kiser PD, Wyss A, Palczewski K, von Lintig J. The Biochemical Basis of Vitamin A3 Production in Arthropod Vision. ACS Chem Biol 2016; 11:1049-57. [PMID: 26811964 PMCID: PMC4841470 DOI: 10.1021/acschembio.5b00967] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Metazoan photochemistry involves cis-trans isomerization of a retinylidene chromophore bound to G protein coupled receptors. Successful production of chromophores is critical for photoreceptor function and survival. For chromophore production, animals have to choose from more than 600 naturally occurring carotenoids and process them by oxidative cleavage and geometric isomerization of double bonds. Vertebrates employ three carotenoid cleavage oxygenases to tailor the carotenoid precursor in the synthesis of 11-cis-retinal (vitamin A1). Lepidoptera (butterfly and moth) possess only one such enzyme, NinaB, which faces the challenge to catalyze these reactions in unison to produce 11-cis-3-hydroxy-retinal (vitamin A3). We here showed that key to this multitasking is a bipartite substrate recognition site that conveys regio- and stereoselectivity for double bond processing. One side performed the specific C11, C12 cis-isomerization and preferentially binds 3-OH-β-ionone rings sites. The other side maintained a trans configuration in the resulting product and preferentially binds noncanonical ionone ring sites. Concurrent binding of carotenoids containing two cyclohexyl rings to both domains is required for specific oxidative cleavage at position C15, C15' of the substrate. The unique reaction sequence follows a dioxygenase mechanism with a carbocation/radical intermediate. This ingenious quality control system guarantees 11-cis-3-hydroxy-retinal production, the essential retinoid for insect (vitamin A3) vision.
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Affiliation(s)
- Darwin Babino
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH 44106
| | - Marcin Golczak
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH 44106
| | - Philip D. Kiser
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH 44106
| | - Adrian Wyss
- Department of Human Nutrition and Health, DSM Nutritional Products, Kaiseraugst 4303, Switzerland
| | - Krzysztof Palczewski
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH 44106
- Cleveland Center for Membrane and Structural Biology, Case Western Reserve University School of Medicine, Cleveland, OH 44106
| | - Johannes von Lintig
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH 44106
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Ahrazem O, Rubio-Moraga A, Berman J, Capell T, Christou P, Zhu C, Gómez-Gómez L. The carotenoid cleavage dioxygenase CCD2 catalysing the synthesis of crocetin in spring crocuses and saffron is a plastidial enzyme. THE NEW PHYTOLOGIST 2016; 209:650-63. [PMID: 26377696 DOI: 10.1111/nph.13609] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2015] [Accepted: 07/21/2015] [Indexed: 05/20/2023]
Abstract
The apocarotenoid crocetin and its glycosylated derivatives, crocins, confer the red colour to saffron. Crocetin biosynthesis in saffron is catalysed by the carotenoid cleavage dioxygenase CCD2 (AIG94929). No homologues have been identified in other plant species due to the very limited presence of crocetin and its derivatives in the plant kingdom. Spring Crocus species with yellow flowers accumulate crocins in the stigma and tepals. Four carotenoid CCDs, namely CaCCD1, CaCCD2 and CaCCD4a/b and CaCCD4c were first cloned and characterized. CaCCD2 was localized in plastids, and a longer CCD2 version, CsCCD2L, was also localized in this compartment. The activity of CaCCD2 was assessed in Escherichia coli and in a stable rice gene function characterization system, demonstrating the production of crocetin in both systems. The expression of all isolated CCDs was evaluated in stigma and tepals at three key developmental stages in relation with apocarotenoid accumulation. CaCCD2 expression parallels crocin accumulation, but C14 apocarotenoids most likely are associated to the CaCCD1 activity in Crocus ancyrensis flowers. The specific CCD2 localization and its membrane interaction will contribute to the development of a better understanding of the mechanism of crocetin biosynthesis and regulation in the chromoplast.
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Affiliation(s)
- Oussama Ahrazem
- Departamento de Ciencia y Tecnología Agroforestal y Genética, Facultad de Farmacia, Instituto Botánico, Universidad de Castilla-La Mancha, Campus Universitario s/n, 02071, Albacete, Spain
- Fundación Parque Científico y Tecnológico de Castilla-La Mancha, Campus Universitario s/n, 02071, Albacete, Spain
| | - Angela Rubio-Moraga
- Departamento de Ciencia y Tecnología Agroforestal y Genética, Facultad de Farmacia, Instituto Botánico, Universidad de Castilla-La Mancha, Campus Universitario s/n, 02071, Albacete, Spain
| | - Judit Berman
- Departament de Producció Vegetal i Ciència Forestal, Universitat de Lleida-Agrotecnio Center, Avenida Alcalde Rovira Roure 191, 25198, Lleida, Spain
| | - Teresa Capell
- Departament de Producció Vegetal i Ciència Forestal, Universitat de Lleida-Agrotecnio Center, Avenida Alcalde Rovira Roure 191, 25198, Lleida, Spain
| | - Paul Christou
- Departament de Producció Vegetal i Ciència Forestal, Universitat de Lleida-Agrotecnio Center, Avenida Alcalde Rovira Roure 191, 25198, Lleida, Spain
- Institució Catalana de Recerca i Estudis Avancats, 08010, Barcelona, Spain
| | - Changfu Zhu
- Departament de Producció Vegetal i Ciència Forestal, Universitat de Lleida-Agrotecnio Center, Avenida Alcalde Rovira Roure 191, 25198, Lleida, Spain
| | - Lourdes Gómez-Gómez
- Departamento de Ciencia y Tecnología Agroforestal y Genética, Facultad de Farmacia, Instituto Botánico, Universidad de Castilla-La Mancha, Campus Universitario s/n, 02071, Albacete, Spain
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Eroglu A, Gentleman S, Poliakov E, Redmond TM. Inhibition of RPE65 Retinol Isomerase Activity by Inhibitors of Lipid Metabolism. J Biol Chem 2015; 291:4966-73. [PMID: 26719343 DOI: 10.1074/jbc.m115.685651] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Indexed: 11/06/2022] Open
Abstract
RPE65 is the isomerase catalyzing conversion of all-trans-retinyl ester (atRE) into 11-cis-retinol in the retinal visual cycle. Crystal structures of RPE65 and site-directed mutagenesis reveal aspects of its catalytic mechanism, especially retinyl moiety isomerization, but other aspects remain to be determined. To investigate potential interactions between RPE65 and lipid metabolism enzymes, HEK293-F cells were transfected with expression vectors for visual cycle proteins and co-transfected with either fatty acyl:CoA ligases (ACSLs) 1, 3, or 6 or the SLC27A family fatty acyl-CoA synthase FATP2/SLCA27A2 to test their effect on isomerase activity. These experiments showed that RPE65 activity was reduced by co-expression of ACSLs or FATP2. Surprisingly, however, in attempting to relieve the ACSL-mediated inhibition, we discovered that triacsin C, an inhibitor of ACSLs, also potently inhibited RPE65 isomerase activity in cellulo. We found triacsin C to be a competitive inhibitor of RPE65 (IC50 = 500 nm). We confirmed that triacsin C competes directly with atRE by incubating membranes prepared from chicken RPE65-transfected cells with liposomes containing 0-1 μM atRE. Other inhibitors of ACSLs had modest inhibitory effects compared with triascin C. In conclusion, we have identified an inhibitor of ACSLs as a potent inhibitor of RPE65 that competes with the atRE substrate of RPE65 for binding. Triacsin C, with an alkenyl chain resembling but not identical to either acyl or retinyl chains, may compete with binding of the acyl moiety of atRE via the alkenyl moiety. Its inhibitory effect, however, may reside in its nitrosohydrazone/triazene moiety.
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Affiliation(s)
- Abdulkerim Eroglu
- From the Laboratory of Retinal Cell & Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892
| | - Susan Gentleman
- From the Laboratory of Retinal Cell & Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892
| | - Eugenia Poliakov
- From the Laboratory of Retinal Cell & Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892
| | - T Michael Redmond
- From the Laboratory of Retinal Cell & Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892
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34
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Sui X, Golczak M, Zhang J, Kleinberg KA, von Lintig J, Palczewski K, Kiser PD. Utilization of Dioxygen by Carotenoid Cleavage Oxygenases. J Biol Chem 2015; 290:30212-23. [PMID: 26499794 PMCID: PMC4683246 DOI: 10.1074/jbc.m115.696799] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Revised: 10/22/2015] [Indexed: 11/06/2022] Open
Abstract
Carotenoid cleavage oxygenases (CCOs) are non-heme, Fe(II)-dependent enzymes that participate in biologically important metabolic pathways involving carotenoids and apocarotenoids, including retinoids, stilbenes, and related compounds. CCOs typically catalyze the cleavage of non-aromatic double bonds by dioxygen (O2) to form aldehyde or ketone products. Expressed only in vertebrates, the RPE65 sub-group of CCOs catalyzes a non-canonical reaction consisting of concerted ester cleavage and trans-cis isomerization of all-trans-retinyl esters. It remains unclear whether the former group of CCOs functions as mono- or di-oxygenases. Additionally, a potential role for O2 in catalysis by the RPE65 group of CCOs has not been evaluated to date. Here, we investigated the pattern of oxygen incorporation into apocarotenoid products of Synechocystis apocarotenoid oxygenase. Reactions performed in the presence of (18)O-labeled water and (18)O2 revealed an unambiguous dioxygenase pattern of O2 incorporation into the reaction products. Substitution of Ala for Thr at position 136 of apocarotenoid oxygenase, a site predicted to govern the mono- versus dioxygenase tendency of CCOs, greatly reduced enzymatic activity without altering the dioxygenase labeling pattern. Reevaluation of the oxygen-labeling pattern of the resveratrol-cleaving CCO, NOV2, previously reported to be a monooxygenase, using a purified enzyme sample revealed that it too is a dioxygenase. We also demonstrated that bovine RPE65 is not dependent on O2 for its cleavage/isomerase activity. In conjunction with prior research, the results of this study resolve key issues regarding the utilization of O2 by CCOs and indicate that dioxygenase activity is a feature common among double bond-cleaving CCOs.
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Affiliation(s)
- Xuewu Sui
- From the Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4956 and
| | - Marcin Golczak
- From the Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4956 and
| | - Jianye Zhang
- From the Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4956 and
| | - Katie A Kleinberg
- From the Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4956 and
| | - Johannes von Lintig
- From the Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4956 and
| | - Krzysztof Palczewski
- From the Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4956 and
| | - Philip D Kiser
- From the Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4956 and the Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio 44106
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35
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Sahu B, Sun W, Perusek L, Parmar V, Le YZ, Griswold MD, Palczewski K, Maeda A. Conditional Ablation of Retinol Dehydrogenase 10 in the Retinal Pigmented Epithelium Causes Delayed Dark Adaption in Mice. J Biol Chem 2015; 290:27239-27247. [PMID: 26391396 DOI: 10.1074/jbc.m115.682096] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Indexed: 12/29/2022] Open
Abstract
Regeneration of the visual chromophore, 11-cis-retinal, is a crucial step in the visual cycle required to sustain vision. This cycle consists of sequential biochemical reactions that occur in photoreceptor cells and the retinal pigmented epithelium (RPE). Oxidation of 11-cis-retinol to 11-cis-retinal is accomplished by a family of enzymes termed 11-cis-retinol dehydrogenases, including RDH5 and RDH11. Double deletion of Rdh5 and Rdh11 does not limit the production of 11-cis-retinal in mice. Here we describe a third retinol dehydrogenase in the RPE, RDH10, which can produce 11-cis-retinal. Mice with a conditional knock-out of Rdh10 in RPE cells (Rdh10 cKO) displayed delayed 11-cis-retinal regeneration and dark adaption after bright light illumination. Retinal function measured by electroretinogram after light exposure was also delayed in Rdh10 cKO mice as compared with controls. Double deletion of Rdh5 and Rdh10 (cDKO) in mice caused elevated 11/13-cis-retinyl ester content also seen in Rdh5(-/-)Rdh11(-/-) mice as compared with Rdh5(-/-) mice. Normal retinal morphology was observed in 6-month-old Rdh10 cKO and cDKO mice, suggesting that loss of Rdh10 in the RPE does not negatively affect the health of the retina. Compensatory expression of other retinol dehydrogenases was observed in both Rdh5(-/-) and Rdh10 cKO mice. These results indicate that RDH10 acts in cooperation with other RDH isoforms to produce the 11-cis-retinal chromophore needed for vision.
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Affiliation(s)
- Bhubanananda Sahu
- Departments of Ophthalmology and Visual Sciences, Case Western Reserve University, School of Medicine, Cleveland, Ohio 44106
| | - Wenyu Sun
- Polgenix, Inc., Cleveland, Ohio 44106
| | - Lindsay Perusek
- Departments of Ophthalmology and Visual Sciences, Case Western Reserve University, School of Medicine, Cleveland, Ohio 44106
| | - Vipulkumar Parmar
- Departments of Ophthalmology and Visual Sciences, Case Western Reserve University, School of Medicine, Cleveland, Ohio 44106
| | - Yun-Zheng Le
- Departments of Medicine Endocrinology, Cell Biology, and Ophthalmology and the Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - Michael D Griswold
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164
| | - Krzysztof Palczewski
- Departments of Pharmacology, Case Western Reserve University, School of Medicine, Cleveland, Ohio 44106; Cleveland Center for Membrane and Structural Biology, Case Western Reserve University, School of Medicine, Cleveland, Ohio 44106
| | - Akiko Maeda
- Departments of Ophthalmology and Visual Sciences, Case Western Reserve University, School of Medicine, Cleveland, Ohio 44106; Departments of Pharmacology, Case Western Reserve University, School of Medicine, Cleveland, Ohio 44106.
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36
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Babino D, Palczewski G, Widjaja-Adhi MAK, Kiser PD, Golczak M, von Lintig J. Characterization of the Role of β-Carotene 9,10-Dioxygenase in Macular Pigment Metabolism. J Biol Chem 2015; 290:24844-57. [PMID: 26307071 DOI: 10.1074/jbc.m115.668822] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Indexed: 12/22/2022] Open
Abstract
A family of enzymes collectively referred to as carotenoid cleavage oxygenases is responsible for oxidative conversion of carotenoids into apocarotenoids, including retinoids (vitamin A and its derivatives). A member of this family, the β-carotene 9,10-dioxygenase (BCO2), converts xanthophylls to rosafluene and ionones. Animals deficient in BCO2 highlight the critical role of the enzyme in carotenoid clearance as accumulation of these compounds occur in tissues. Inactivation of the enzyme by a four-amino acid-long insertion has recently been proposed to underlie xanthophyll concentration in the macula of the primate retina. Here, we focused on comparing the properties of primate and murine BCO2s. We demonstrate that the enzymes display a conserved structural fold and subcellular localization. Low temperature expression and detergent choice significantly affected binding and turnover rates of the recombinant enzymes with various xanthophyll substrates, including the unique macula pigment meso-zeaxanthin. Mice with genetically disrupted carotenoid cleavage oxygenases displayed adipose tissue rather than eye-specific accumulation of supplemented carotenoids. Studies in a human hepatic cell line revealed that BCO2 is expressed as an oxidative stress-induced gene. Our studies provide evidence that the enzymatic function of BCO2 is conserved in primates and link regulation of BCO2 gene expression with oxidative stress that can be caused by excessive carotenoid supplementation.
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Affiliation(s)
- Darwin Babino
- From the Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106 and
| | - Grzegorz Palczewski
- From the Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106 and
| | - M Airanthi K Widjaja-Adhi
- From the Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106 and
| | - Philip D Kiser
- From the Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106 and the Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio 44106
| | - Marcin Golczak
- From the Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106 and
| | - Johannes von Lintig
- From the Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106 and
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Kiser PD, Zhang J, Badiee M, Li Q, Shi W, Sui X, Golczak M, Tochtrop GP, Palczewski K. Catalytic mechanism of a retinoid isomerase essential for vertebrate vision. Nat Chem Biol 2015; 11:409-15. [PMID: 25894083 PMCID: PMC4433804 DOI: 10.1038/nchembio.1799] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Accepted: 03/24/2015] [Indexed: 11/20/2022]
Abstract
Visual function in vertebrates is dependent on the membrane-bound retinoid isomerase RPE65, an essential component of the retinoid cycle pathway that regenerates 11-cis-retinal for rod and cone opsins. The mechanism by which RPE65 catalyzes stereoselective retinoid isomerization has remained elusive because of uncertainty about how retinoids bind to its active site. Here we present crystal structures of RPE65 in complex with retinoid-mimetic compounds, one of which is in clinical trials for the treatment of age-related macular degeneration. The structures reveal the active site retinoid-binding cavity located near the membrane-interacting surface of the enzyme as well as an Fe-bound palmitate ligand positioned in an adjacent pocket. With the geometry of the RPE65-substrate complex clarified, we delineate a mechanism of catalysis that reconciles the extensive biochemical and structural research on this enzyme. These data provide molecular foundations for understanding a key process in vision and pharmacological inhibition of RPE65 with small molecules.
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Affiliation(s)
- Philip D. Kiser
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106
| | - Jianye Zhang
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106
| | - Mohsen Badiee
- Department of Chemistry, Case Western Reserve University, Cleveland, OH 44106
| | - Qingjiang Li
- Department of Chemistry, Case Western Reserve University, Cleveland, OH 44106
| | - Wuxian Shi
- National Synchrotron Light Source, Brookhaven National Laboratory, Upton, NY 11973
- Case Center for Synchrotron Biosciences, School of Medicine, Case Western Reserve University, Cleveland, OH 44106
| | - Xuewu Sui
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106
| | - Marcin Golczak
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106
| | - Gregory P. Tochtrop
- Department of Chemistry, Case Western Reserve University, Cleveland, OH 44106
| | - Krzysztof Palczewski
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106
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Li S, Hu J, Jin RJ, Aiyar A, Jacobson SG, Bok D, Jin M. Temperature-sensitive retinoid isomerase activity of RPE65 mutants associated with Leber Congenital Amaurosis. J Biochem 2015; 158:115-25. [PMID: 25752820 DOI: 10.1093/jb/mvv028] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2014] [Accepted: 01/26/2015] [Indexed: 12/22/2022] Open
Abstract
RPE65 is a membrane-associated retinoid isomerase involved in the visual cycle responsible for sustaining vision. Many mutations in the human RPE65 gene are associated with distinct forms of retinal degenerative diseases. The pathogenic mechanisms for most of these mutations remain poorly understood. Here, we show that three Leber congenital amaurosis -associated RPE65 mutants (R91W, Y249C and R515W) undergo rapid proteasomal degradation mediated by the 26 S proteasome non-ATPase regulatory subunit 13 (PSMD13) in cultured human retinal pigment epithelium (RPE) cells. These mutant proteins formed cytosolic inclusion bodies or high molecular weight complexes via disulfide bonds. The mutations are mapped on non-active sites but severely reduced isomerase activity of RPE65. At 30°C, however, the enzymatic function and membrane-association of the mutant RPE65s are significantly rescued possibly due to proper folding. In addition, PSMD13 displayed a drastically decreased effect on degradation of the mutant proteins in the cells grown at 30°C. These results suggest that PSMD13 plays a critical role in regulating pathogenicity of the mutations and the molecular basis for the PSMD13-mediated rapid degradation and loss of function of the mutants is misfolding of RPE65.
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Affiliation(s)
- Songhua Li
- Department of Ophthalmology and Neuroscience Center, Louisiana State University Health Sciences Center, New Orleans, LA 70112 USA
| | - Jane Hu
- Jules Stein Eye Institute and Department of Neurobiology, University of California, Los Angeles, CA 90095 USA
| | - Robin J Jin
- State University of New York at Buffalo, Buffalo, NY 14214 USA
| | - Ashok Aiyar
- Department of Microbiology, Immunology and Parasitology, Louisiana State University Health Sciences Center, New Orleans, LA 70112 USA; and
| | - Samuel G Jacobson
- Scheie Eye Institute, University of Pennsylvania, Philadelphia, PA 19104 USA
| | - Dean Bok
- Jules Stein Eye Institute and Department of Neurobiology, University of California, Los Angeles, CA 90095 USA
| | - Minghao Jin
- Department of Ophthalmology and Neuroscience Center, Louisiana State University Health Sciences Center, New Orleans, LA 70112 USA;
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Wright CB, Redmond TM, Nickerson JM. A History of the Classical Visual Cycle. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2015; 134:433-48. [DOI: 10.1016/bs.pmbts.2015.06.009] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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40
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Zhang J, Dong Z, Mundla SR, Hu XE, Seibel W, Papoian R, Palczewski K, Golczak M. Expansion of first-in-class drug candidates that sequester toxic all-trans-retinal and prevent light-induced retinal degeneration. Mol Pharmacol 2014; 87:477-91. [PMID: 25538117 DOI: 10.1124/mol.114.096560] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
All-trans-retinal, a retinoid metabolite naturally produced upon photoreceptor light activation, is cytotoxic when present at elevated levels in the retina. To lower its toxicity, two experimentally validated methods have been developed involving inhibition of the retinoid cycle and sequestration of excess of all-trans-retinal by drugs containing a primary amine group. We identified the first-in-class drug candidates that transiently sequester this metabolite or slow down its production by inhibiting regeneration of the visual chromophore, 11-cis-retinal. Two enzymes are critical for retinoid recycling in the eye. Lecithin:retinol acyltransferase (LRAT) is the enzyme that traps vitamin A (all-trans-retinol) from the circulation and photoreceptor cells to produce the esterified substrate for retinoid isomerase (RPE65), which converts all-trans-retinyl ester into 11-cis-retinol. Here we investigated retinylamine and its derivatives to assess their inhibitor/substrate specificities for RPE65 and LRAT, mechanisms of action, potency, retention in the eye, and protection against acute light-induced retinal degeneration in mice. We correlated levels of visual cycle inhibition with retinal protective effects and outlined chemical boundaries for LRAT substrates and RPE65 inhibitors to obtain critical insights into therapeutic properties needed for retinal preservation.
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Affiliation(s)
- Jianye Zhang
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio (J.Z., Z.D., K.P., M.G.); Sreeni Laboratories Private Limited, Telangana, India (S.R.M.); Aroz Technologies LLC, Cincinnati, Ohio (X.E.H.); and Drug Discovery Center, College of Medicine, University of Cincinnati, Cincinnati, Ohio (W.S., R.P.)
| | - Zhiqian Dong
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio (J.Z., Z.D., K.P., M.G.); Sreeni Laboratories Private Limited, Telangana, India (S.R.M.); Aroz Technologies LLC, Cincinnati, Ohio (X.E.H.); and Drug Discovery Center, College of Medicine, University of Cincinnati, Cincinnati, Ohio (W.S., R.P.)
| | - Sreenivasa Reddy Mundla
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio (J.Z., Z.D., K.P., M.G.); Sreeni Laboratories Private Limited, Telangana, India (S.R.M.); Aroz Technologies LLC, Cincinnati, Ohio (X.E.H.); and Drug Discovery Center, College of Medicine, University of Cincinnati, Cincinnati, Ohio (W.S., R.P.)
| | - X Eric Hu
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio (J.Z., Z.D., K.P., M.G.); Sreeni Laboratories Private Limited, Telangana, India (S.R.M.); Aroz Technologies LLC, Cincinnati, Ohio (X.E.H.); and Drug Discovery Center, College of Medicine, University of Cincinnati, Cincinnati, Ohio (W.S., R.P.)
| | - William Seibel
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio (J.Z., Z.D., K.P., M.G.); Sreeni Laboratories Private Limited, Telangana, India (S.R.M.); Aroz Technologies LLC, Cincinnati, Ohio (X.E.H.); and Drug Discovery Center, College of Medicine, University of Cincinnati, Cincinnati, Ohio (W.S., R.P.)
| | - Ruben Papoian
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio (J.Z., Z.D., K.P., M.G.); Sreeni Laboratories Private Limited, Telangana, India (S.R.M.); Aroz Technologies LLC, Cincinnati, Ohio (X.E.H.); and Drug Discovery Center, College of Medicine, University of Cincinnati, Cincinnati, Ohio (W.S., R.P.)
| | - Krzysztof Palczewski
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio (J.Z., Z.D., K.P., M.G.); Sreeni Laboratories Private Limited, Telangana, India (S.R.M.); Aroz Technologies LLC, Cincinnati, Ohio (X.E.H.); and Drug Discovery Center, College of Medicine, University of Cincinnati, Cincinnati, Ohio (W.S., R.P.)
| | - Marcin Golczak
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio (J.Z., Z.D., K.P., M.G.); Sreeni Laboratories Private Limited, Telangana, India (S.R.M.); Aroz Technologies LLC, Cincinnati, Ohio (X.E.H.); and Drug Discovery Center, College of Medicine, University of Cincinnati, Cincinnati, Ohio (W.S., R.P.)
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Palczewski K. Chemistry and biology of the initial steps in vision: the Friedenwald lecture. Invest Ophthalmol Vis Sci 2014; 55:6651-72. [PMID: 25338686 DOI: 10.1167/iovs.14-15502] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Visual transduction is the process in the eye whereby absorption of light in the retina is translated into electrical signals that ultimately reach the brain. The first challenge presented by visual transduction is to understand its molecular basis. We know that maintenance of vision is a continuous process requiring the activation and subsequent restoration of a vitamin A-derived chromophore through a series of chemical reactions catalyzed by enzymes in the retina and retinal pigment epithelium (RPE). Diverse biochemical approaches that identified key proteins and reactions were essential to achieve a mechanistic understanding of these visual processes. The three-dimensional arrangements of these enzymes' polypeptide chains provide invaluable insights into their mechanisms of action. A wealth of information has already been obtained by solving high-resolution crystal structures of both rhodopsin and the retinoid isomerase from pigment RPE (RPE65). Rhodopsin, which is activated by photoisomerization of its 11-cis-retinylidene chromophore, is a prototypical member of a large family of membrane-bound proteins called G protein-coupled receptors (GPCRs). RPE65 is a retinoid isomerase critical for regeneration of the chromophore. Electron microscopy (EM) and atomic force microscopy have provided insights into how certain proteins are assembled to form much larger structures such as rod photoreceptor cell outer segment membranes. A second challenge of visual transduction is to use this knowledge to devise therapeutic approaches that can prevent or reverse conditions leading to blindness. Imaging modalities like optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO) applied to appropriate animal models as well as human retinal imaging have been employed to characterize blinding diseases, monitor their progression, and evaluate the success of therapeutic agents. Lately two-photon (2-PO) imaging, together with biochemical assays, are revealing functional aspects of vision at a new molecular level. These multidisciplinary approaches combined with suitable animal models and inbred mutant species can be especially helpful in translating provocative cell and tissue culture findings into therapeutic options for further development in animals and eventually in humans. A host of different approaches and techniques is required for substantial progress in understanding fundamental properties of the visual system.
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Affiliation(s)
- Krzysztof Palczewski
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, United States
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42
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Palczewski G, Amengual J, Hoppel CL, von Lintig J. Evidence for compartmentalization of mammalian carotenoid metabolism. FASEB J 2014; 28:4457-69. [PMID: 25002123 DOI: 10.1096/fj.14-252411] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The critical role of retinoids (vitamin A and its derivatives) for vision, reproduction, and survival has been well established. Vitamin A is produced from dietary carotenoids such as β-carotene by centric cleavage via the enzyme BCO1. The biochemical and molecular identification of a second structurally related β-carotene metabolizing enzyme, BCO2, has led to a prolonged debate about its relevance in vitamin A biology. While BCO1 cleaves provitamin A carotenoids, BCO2 is more promiscuous and also metabolizes nonprovitamin A carotenoids such as zeaxanthin into long-chain apo-carotenoids. Herein we demonstrate, in cell lines, that human BCO2 is associated with the inner mitochondrial membrane. Different human BCO2 isoforms possess cleavable N-terminal leader sequences critical for mitochondrial import. Subfractionation of murine hepatic mitochondria confirmed the localization of BCO2 to the inner mitochondrial membrane. Studies in BCO2-knockout mice revealed that zeaxanthin accumulates in the inner mitochondrial membrane; in contrast, β-carotene is retained predominantly in the cytoplasm. Thus, we provide evidence for a compartmentalization of carotenoid metabolism that prevents competition between BCO1 and BCO2 for the provitamin and the production of noncanonical β-carotene metabolites.
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Affiliation(s)
| | | | - Charles L Hoppel
- Department of Pharmacology, and Department of Medicine, School of Medicine, Case Western Reserve University, Cleveland, Ohio, USA
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43
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Li S, Izumi T, Hu J, Jin HH, Siddiqui AAA, Jacobson SG, Bok D, Jin M. Rescue of enzymatic function for disease-associated RPE65 proteins containing various missense mutations in non-active sites. J Biol Chem 2014; 289:18943-56. [PMID: 24849605 PMCID: PMC4081934 DOI: 10.1074/jbc.m114.552117] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Over 70 different missense mutations, including a dominant mutation, in RPE65 retinoid isomerase are associated with distinct forms of retinal degeneration; however, the disease mechanisms for most of these mutations have not been studied. Although some mutations have been shown to abolish enzyme activity, the molecular mechanisms leading to the loss of enzymatic function and retinal degeneration remain poorly understood. Here we show that the 26 S proteasome non-ATPase regulatory subunit 13 (PSMD13), a newly identified negative regulator of RPE65, plays a critical role in regulating pathogenicity of three mutations (L22P, T101I, and L408P) by mediating rapid degradation of mutated RPE65s via a ubiquitination- and proteasome-dependent non-lysosomal pathway. These mutant RPE65s were misfolded and formed aggregates or high molecular complexes via disulfide bonds. Interaction of PSMD13 with mutant RPE65s promoted degradation of misfolded but not properly folded mutant RPE65s. Many mutations, including L22P, T101I, and L408P, were mapped on non-active sites. Although their activities were very low, these mutant RPE65s were catalytically active and could be significantly rescued at low temperature, whereas mutant RPE65s with a distinct active site mutation could not be rescued under the same conditions. Sodium 4-phenylbutyrate and glycerol displayed a significant synergistic effect on the low temperature rescue of the mutant RPE65s by promoting proper folding, reducing aggregation, and increasing membrane association. Our results suggest that a low temperature eye mask and sodium 4-phenylbutyrate, a United States Food and Drug Administration-approved oral medicine, may provide a promising "protein repair therapy" that can enhance the efficacy of gene therapy by reducing the cytotoxic effect of misfolded mutant RPE65s.
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Affiliation(s)
- Songhua Li
- From the Department of Ophthalmology and Neuroscience Center, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112
| | - Tadahide Izumi
- Graduate Center for Toxicology, University of Kentucky College of Medicine, Lexington, Kentucky 40536
| | - Jane Hu
- Jules Stein Eye Institute and Department of Neurobiology, University of California, Los Angeles, California 90095
| | - Heather H Jin
- Department of Biology, Washington University, St. Louis, Missouri 63130
| | | | - Samuel G Jacobson
- Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Dean Bok
- Jules Stein Eye Institute and Department of Neurobiology, University of California, Los Angeles, California 90095
| | - Minghao Jin
- From the Department of Ophthalmology and Neuroscience Center, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112,
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44
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Sui X, Kiser PD, Che T, Carey PR, Golczak M, Shi W, von Lintig J, Palczewski K. Analysis of carotenoid isomerase activity in a prototypical carotenoid cleavage enzyme, apocarotenoid oxygenase (ACO). J Biol Chem 2014; 289:12286-99. [PMID: 24648526 PMCID: PMC4007427 DOI: 10.1074/jbc.m114.552836] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Revised: 02/19/2014] [Indexed: 11/06/2022] Open
Abstract
Carotenoid cleavage enzymes (CCEs) constitute a group of evolutionarily related proteins that metabolize a variety of carotenoid and non-carotenoid substrates. Typically, these enzymes utilize a non-heme iron center to oxidatively cleave a carbon-carbon double bond of a carotenoid substrate. Some members also isomerize specific double bonds in their substrates to yield cis-apocarotenoid products. The apocarotenoid oxygenase from Synechocystis has been hypothesized to represent one such member of this latter category of CCEs. Here, we developed a novel expression and purification protocol that enabled production of soluble, native ACO in quantities sufficient for high resolution structural and spectroscopic investigation of its catalytic mechanism. High performance liquid chromatography and Raman spectroscopy revealed that ACO exclusively formed all-trans products. We also found that linear polyoxyethylene detergents previously used for ACO crystallization strongly inhibited the apocarotenoid oxygenase activity of the enzyme. We crystallized the native enzyme in the absence of apocarotenoid substrate and found electron density in the active site that was similar in appearance to the density previously attributed to a di-cis-apocarotenoid intermediate. Our results clearly demonstrated that ACO is in fact a non-isomerizing member of the CCE family. These results indicate that careful selection of detergent is critical for the success of structural studies aimed at elucidating structures of CCE-carotenoid/retinoid complexes.
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Affiliation(s)
- Xuewu Sui
- From the Departments of Pharmacology and
| | | | - Tao Che
- Biochemistry, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4965 and
| | - Paul R. Carey
- Biochemistry, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4965 and
| | | | - Wuxian Shi
- the Center for Proteomics and Bioinformatics, Center for Synchrotron Biosciences, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4988
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Affiliation(s)
| | | | - Krzysztof Palczewski
- Department of Pharmacology, School of Medicine, Case
Western Reserve University, 2109 Adelbert Road, Cleveland, Ohio 44106-4965,
United States
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46
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Bolze CS, Helbling RE, Owen RL, Pearson AR, Pompidor G, Dworkowski F, Fuchs MR, Furrer J, Golczak M, Palczewski K, Cascella M, Stocker A. Human cellular retinaldehyde-binding protein has secondary thermal 9-cis-retinal isomerase activity. J Am Chem Soc 2013; 136:137-46. [PMID: 24328211 DOI: 10.1021/ja411366w] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Cellular retinaldehyde-binding protein (CRALBP) chaperones 11-cis-retinal to convert opsin receptor molecules into photosensitive retinoid pigments of the eye. We report a thermal secondary isomerase activity of CRALBP when bound to 9-cis-retinal. UV/vis and (1)H NMR spectroscopy were used to characterize the product as 9,13-dicis-retinal. The X-ray structure of the CRALBP mutant R234W:9-cis-retinal complex at 1.9 Å resolution revealed a niche in the binding pocket for 9-cis-aldehyde different from that reported for 11-cis-retinal. Combined computational, kinetic, and structural data lead us to propose an isomerization mechanism catalyzed by a network of buried waters. Our findings highlight a specific role of water molecules in both CRALBP-assisted specificity toward 9-cis-retinal and its thermal isomerase activity yielding 9,13-dicis-retinal. Kinetic data from two point mutants of CRALBP support an essential role of Glu202 as the initial proton donor in this isomerization reaction.
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Affiliation(s)
- Christin S Bolze
- Department of Chemistry and Biochemistry, and ‡Graduate School for Cellular and Biomedical Sciences, University of Bern , Freiestrasse 3, 3012 Bern, Switzerland
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47
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Orban T, Jastrzebska B, Palczewski K. Structural approaches to understanding retinal proteins needed for vision. Curr Opin Cell Biol 2013; 27:32-43. [PMID: 24680428 DOI: 10.1016/j.ceb.2013.11.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Revised: 10/31/2013] [Accepted: 11/01/2013] [Indexed: 12/21/2022]
Abstract
The past decade has witnessed an impressive expansion of our knowledge of retinal photoreceptor signal transduction and the regulation of the visual cycle required for normal eyesight. Progress in human genetics and next generation sequencing technologies have revealed the complexity behind many inherited retinal diseases. Structural studies have markedly increased our understanding of the visual process. Moreover, technical innovations and improved methodologies in proteomics, macromolecular crystallization and high resolution imaging at different levels set the scene for even greater advances. Pharmacology combined with structural biology of membrane proteins holds great promise for developing innovative accessible therapies for millions robbed of their sight or progressing toward blindness.
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Affiliation(s)
- Tivadar Orban
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Beata Jastrzebska
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Krzysztof Palczewski
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH 44106, USA.
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Sui X, Kiser PD, von Lintig J, Palczewski K. Structural basis of carotenoid cleavage: from bacteria to mammals. Arch Biochem Biophys 2013; 539:203-13. [PMID: 23827316 PMCID: PMC3818509 DOI: 10.1016/j.abb.2013.06.012] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Revised: 06/12/2013] [Accepted: 06/13/2013] [Indexed: 10/26/2022]
Abstract
Carotenoids and their metabolic derivatives serve critical functions in both prokaryotic and eukaryotic cells, including pigmentation, photoprotection and photosynthesis as well as cell signaling. These organic compounds are also important for visual function in vertebrate and non-vertebrate organisms. Enzymatic transformations of carotenoids to various apocarotenoid products are catalyzed by a family of evolutionarily conserved, non-heme iron-containing enzymes named carotenoid cleavage oxygenases (CCOs). Studies have revealed that CCOs are critically involved in carotenoid homeostasis and essential for the health of organisms including humans. These enzymes typically display a high degree of regio- and stereo-selectivity, acting on specific positions of the polyene backbone located in their substrates. By oxidatively cleaving and/or isomerizing specific double bonds, CCOs generate a variety of apocarotenoid isomer products. Recent structural studies have helped illuminate the mechanisms by which CCOs mobilize their lipophilic substrates from biological membranes to perform their characteristic double bond cleavage and/or isomerization reactions. In this review, we aim to integrate structural and biochemical information about CCOs to provide insights into their catalytic mechanisms.
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Affiliation(s)
- Xuewu Sui
- Department of Pharmacology, School of Medicine, Case Western Reserve University, 2109 Adelbert Rd, Cleveland, OH 44106-4965, USA
| | - Philip D. Kiser
- Department of Pharmacology, School of Medicine, Case Western Reserve University, 2109 Adelbert Rd, Cleveland, OH 44106-4965, USA
| | - Johannes von Lintig
- Department of Pharmacology, School of Medicine, Case Western Reserve University, 2109 Adelbert Rd, Cleveland, OH 44106-4965, USA
| | - Krzysztof Palczewski
- Department of Pharmacology, School of Medicine, Case Western Reserve University, 2109 Adelbert Rd, Cleveland, OH 44106-4965, USA
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Kowatz T, Babino D, Kiser P, Palczewski K, von Lintig J. Characterization of human β,β-carotene-15,15'-monooxygenase (BCMO1) as a soluble monomeric enzyme. Arch Biochem Biophys 2013; 539:214-22. [PMID: 23727499 PMCID: PMC3795993 DOI: 10.1016/j.abb.2013.05.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Revised: 05/13/2013] [Accepted: 05/14/2013] [Indexed: 11/19/2022]
Abstract
The formal first step in in vitamin A metabolism is the conversion of its natural precursor β,β-carotene (C40) to retinaldehyde (C20). This reaction is catalyzed by the enzyme β,β-carotene-15,15'-monooxygenase (BCMO1). BCMO1 has been cloned from several vertebrate species, including humans. However, knowledge about this protein's enzymatic and structural properties is scant. Here we expressed human BCMO1 in Spodoptera frugiperda 9 insect cells. Recombinant BCMO1 is a soluble protein that displayed Michaelis-Menten kinetics with a KM of 14 μM for β,β-carotene. Though addition of detergents failed to increase BCMO1 enzymatic activity, short chain aliphatic detergents such as C8E4 and C8E6 decreased enzymatic activity probably by interacting with the substrate binding site. Thus we purified BCMO1 in the absence of detergent. Purified BCMO1 was a monomeric enzymatically active soluble protein that did not require cofactors and displayed a turnover rate of about 8 molecules of β,β-carotene per second. The aqueous solubility of BCMO1 was confirmed in mouse liver and mammalian cells. Establishment of a protocol that yields highly active homogenous BCMO1 is an important step towards clarifying the lipophilic substrate interaction, reaction mechanism and structure of this vitamin A forming enzyme.
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Affiliation(s)
- Thomas Kowatz
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
| | - Darwin Babino
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
| | - Philip Kiser
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
| | - Krzysztof Palczewski
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
| | - Johannes von Lintig
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
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Wright CB, Chrenek MA, Foster SL, Duncan T, Redmond TM, Pardue MT, Boatright JH, Nickerson JM. Complementation test of Rpe65 knockout and tvrm148. Invest Ophthalmol Vis Sci 2013; 54:5111-22. [PMID: 23778877 DOI: 10.1167/iovs.13-12336] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE A mouse mutation, tvrm148, was previously reported as resulting in retinal degeneration. Tvrm148 and Rpe65 map between markers D3Mit147 and D3Mit19 on a genetic map, but the physical map places RPE65 outside the markers. We asked if Rpe65 or perhaps another nearby gene is mutated and if the mutant reduced 11-cis-retinal levels. We studied the impact of the tvrm148 mutation on visual function, morphology, and retinoid levels. METHODS Normal phase HPLC was used to measure retinoid levels. Rpe65(+/+), tvrm148/+ (T(+/-)), tvrm148/tvrm148 (T(-/-)), RPE65(KO/KO) (Rpe65(-/-)), and Rpe65(T/-) mice visual function was measured by optokinetic tracking (OKT) and electroretinography (ERG). Morphology was assessed by light microscopy and transmission electron microscopy (TEM). qRT-PCR was used to measure Rpe65 mRNA levels. Immunoblotting measured the size and amount of RPE65 protein. RESULTS The knockout and tvrm148 alleles did not complement. No 11-cis-retinal was detected in T(-/-) or Rpe65(-/-) mice. Visual acuity in Rpe65(+/+) and T(+/-) mouse was -0.382 c/d, but 0.037 c/d in T(-/-) mice at postnatal day 210 (P210). ERG response in T(-/-) mice was undetectable except at bright flash intensities. Outer nuclear layer (ONL) thickness in T(-/-) mice was -70% of Rpe65(+/+) by P210. Rpe65 mRNA levels in T(-/-) mice were unchanged, yet 14.5% of Rpe65(+/+) protein levels was detected. Protein size was unchanged. CONCLUSIONS A complementation test revealed the RPE65 knockout and tvrm148 alleles do not complement, proving that the tvrm148 mutation is in Rpe65. Behavioral, physiological, molecular, biochemical, and histological approaches indicate that tvrm148 is a null allele of Rpe65.
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Affiliation(s)
- Charles B Wright
- Department of Ophthalmology, School of Medicine, Emory University, Atlanta, Georgia 30322, USA
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