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Vendra VPR, Ostrowski C, Clark R, Dyba M, Tarasov SG, Hejtmancik JF. The Y46D Mutation Destabilizes Dense Packing of the Second Greek Key Pair of Human γC-Crystallin Causing Congenital Nuclear Cataracts. Biochemistry 2023; 62:1864-1877. [PMID: 37184593 PMCID: PMC10758276 DOI: 10.1021/acs.biochem.2c00628] [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] [Indexed: 05/16/2023]
Abstract
The γ-crystallins are highly expressed structural lens proteins comprising four Greek key motifs arranged in two domains. Their globular structure and short-range spatial ordering are essential for lens transparency. Aromatic residues play a vital role in stabilizing Greek key folds by forming Greek key or non-Greek key pairs or tyrosine corners. We investigated the effects of the cataractogenic Y46D mutation in the second Greek key pair (Y46-Y51) of human γC-crystallin on its stability and aggregation. Wild-type and Y46D mutant human γC-crystallin were overexpressed in E. coli BL-21(DE3) PLysS cells, purified using ion-exchange and size-exclusion chromatography, and analyzed by fluorescence spectroscopy and circular dichroism spectroscopy. The Y46D mutation does not affect the γC-crystallin backbone conformation under benign conditions but alters the tryptophan microenvironment, exposing hydrophobic residues to the surface. The Y46D mutant undergoes a three-state transition under thermal stress with midpoints of 54.6 and 67.7 °C while the wild type shows a two-state transition with a midpoint of 77.6 °C. The Y46D mutant also shows a three-state transition under GuHCl stress with Cm values of 0.9 and 2.1 M while the wild type shows a two-state transition with a Cm of 2.4 M GuHCl. Mutant but not wild-type γC-crystallin forms light scattering particles upon heating at 65 °C. Overall, the Y46D CRYGS mutation leaves the protein fold intact under benign conditions but destabilizes the molecule by altering the tryptophan microenvironment and exposing hydrophobic residues to its surface, thus increasing its susceptibility to thermal and chemical stress with resultant self-aggregation, light scattering, and cataract.
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Affiliation(s)
- Venkata Pulla Rao Vendra
- Ophthalmic Molecular Genetics Section, Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20852, United States
| | - Christian Ostrowski
- Ophthalmic Molecular Genetics Section, Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20852, United States
| | - Rebecca Clark
- Ophthalmic Molecular Genetics Section, Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20852, United States
| | - Marzena Dyba
- Biophysics Resource in the Center for Structural Biology, National Cancer Institute, National Institutes of Health, Frederick, Maryland 21702-4091, United States
| | - Sergey G Tarasov
- Biophysics Resource in the Center for Structural Biology, National Cancer Institute, National Institutes of Health, Frederick, Maryland 21702-4091, United States
| | - J Fielding Hejtmancik
- Ophthalmic Molecular Genetics Section, Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20852, United States
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Domínguez-Calva JA, Pérez-Vázquez ML, Serebryany E, King JA, Quintanar L. Mercury-induced aggregation of human lens γ-crystallins reveals a potential role in cataract disease. J Biol Inorg Chem 2018; 23:1105-1118. [DOI: 10.1007/s00775-018-1607-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2018] [Accepted: 08/22/2018] [Indexed: 01/17/2023]
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Khan MS, Bhat SA, Tabrez S, Alama MN, Alsenaidy MA, Al-Senaidy AM. Denaturation induced aggregation in α-crystallin: differential action of chaotropes. J Mol Recognit 2016; 29:536-543. [DOI: 10.1002/jmr.2553] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Revised: 04/21/2016] [Accepted: 05/04/2016] [Indexed: 11/05/2022]
Affiliation(s)
- Mohd Shahnawaz Khan
- Protein Research Chair, Department of Biochemistry, College of Science; King Saud University; Riyadh Saudi Arabia
| | - Sheraz Ahmad Bhat
- Department of Biochemistry, Faculty of Life Sciences; Aligarh Muslim University; Aligarh India
| | - Shams Tabrez
- King Fahd Medical Research Center; King Abdulaziz University; Jeddah 21589 Saudi Arabia
| | - Mohammed Nabil Alama
- Cardiology Unit, Department of Medicine; King Abdulaziz University Hospital; Jeddah 21589 Saudi Arabia
| | - Mohammad A. Alsenaidy
- Department of Pharmaceutics, College of Pharmacy; King Saud University; Riyadh Saudi Arabia
| | - Abdulrahman M. Al-Senaidy
- Protein Research Chair, Department of Biochemistry, College of Science; King Saud University; Riyadh Saudi Arabia
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Dixit K, Pande A, Pande J, Sarma SP. Nuclear Magnetic Resonance Structure of a Major Lens Protein, Human γC-Crystallin: Role of the Dipole Moment in Protein Solubility. Biochemistry 2016; 55:3136-49. [PMID: 27187112 DOI: 10.1021/acs.biochem.6b00359] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A hallmark of the crystallin proteins is their exceptionally high solubility, which is vital for maintaining the high refractive index of the eye lens. Human γC-crystallin is a major γ-crystallin whose mutant forms are associated with congenital cataracts but whose three-dimensional structure is not known. An earlier study of a homology model concluded that human γC-crystallin has low intrinsic solubility, mainly because of the atypical magnitude and fluctuations of its dipole moment. On the contrary, the high-resolution tertiary structure of human γC-crystallin determined here shows unequivocally that it is a highly soluble, monomeric molecule in solution. Notable differences between the orientations and interactions of several side chains are observed upon comparison to those in the model. No evidence of the pivotal role ascribed to the effect of dipole moment on protein solubility was found. The nuclear magnetic resonance structure should facilitate a comprehensive understanding of the deleterious effects of cataract-associated mutations in human γC-crystallin.
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Affiliation(s)
- Karuna Dixit
- Molecular Biophysics Unit, Indian Institute of Science , Bangalore, Karnataka 560012, India
| | - Ajay Pande
- Department of Chemistry, University at Albany, State University of New York , Albany, New York 12222, United States
| | - Jayanti Pande
- Department of Chemistry, University at Albany, State University of New York , Albany, New York 12222, United States
| | - Siddhartha P Sarma
- Molecular Biophysics Unit, Indian Institute of Science , Bangalore, Karnataka 560012, India
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Shao DW, Yang CY, Liu B, Chen W, Wang H, Ru HX, Zhang M, Wang Y. Bioinformatics Analysis of Potential Candidates for Therapy of TDRD7 Deficiency-Induced Congenital Cataract. Ophthalmic Res 2015; 54:10-7. [PMID: 25997407 DOI: 10.1159/000381478] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 03/05/2015] [Indexed: 11/19/2022]
Abstract
AIMS The aim of this study was to identify potential candidates and explore the possible mechanism in congenital cataract induced by tudor domain-containing 7 (TDRD7) deficiency. METHODS The gene expression profile GSE25812 generated from 18 samples was downloaded from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) between disease and normal groups were identified. Then, gene ontology and pathway enrichment analysis of DEGs were performed. The protein-protein interaction (PPI) network and transcription factor (TF) regulatory network were constructed. The modules in the PPI network were identified. Significant target genes were selected from the TF regulatory network. RESULTS A total of 329 DEGs were obtained, and downregulated DEGs were significantly enriched in biological processes including defense response and immune response. In the PPI network, high-degree genes of complement component 1, q subcomponent, A/B/C chain (C1QA/C1QB/C1QC), lymphocyte antigen 86 (LY86) and neuroblastoma RAS viral oncogene homolog (NRAS) were identified. From the TF regulatory network, the heat shock 27 kDa protein 1 (HSPB1) was the target of the estrogen receptor 1, and LY86 was the target of the v-myc avian myelocytomatosis viral oncogene homolog. CONCLUSION HSPB1, NRAS, immune response, defense response and the related genes LY86, C1QA/C1QB/C1QC may play an important role in the development of congenital cataract induced by TDRD7 deficiency. However, further experiments are still needed.
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Affiliation(s)
- De-Wang Shao
- Department of Ophthalmology, Air Force General Hospital of PLA, Beijing, China
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6
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The importance of the last strand at the C-terminus in βB2-crystallin stability and assembly. Biochim Biophys Acta Mol Basis Dis 2014; 1842:44-55. [DOI: 10.1016/j.bbadis.2013.10.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Revised: 09/29/2013] [Accepted: 10/01/2013] [Indexed: 01/15/2023]
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7
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Ji F, Jung J, Koharudin LMI, Gronenborn AM. The human W42R γD-crystallin mutant structure provides a link between congenital and age-related cataracts. J Biol Chem 2012; 288:99-109. [PMID: 23124202 DOI: 10.1074/jbc.m112.416354] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Some mutants of human γD-crystallin are closely linked to congenital cataracts, although the detailed molecular mechanisms of mutant-associated cataract formation are generally not known. Here we report on a recently discovered γD-crystallin mutant (W42R) that has been linked to autosomal dominant, congenital cataracts in a Chinese family. The mutant protein is much less soluble and stable than wild-type γD-crystallin. We solved the crystal structure of W42R at 1.7 Å resolution, which revealed only minor differences from the wild-type structure. Interestingly, the W42R variant is highly susceptible to protease digestion, suggesting the presence of a small population of partially unfolded protein. This partially unfolded species was confirmed and quantified by NMR spectroscopy. Hydrogen/deuterium exchange experiments revealed chemical exchange between the folded and unfolded species. Exposure of wild-type γD-crystallin to UV caused damage to the N-terminal domain of the protein, resulting in very similar proteolytic susceptibility as observed for the W42R mutant. Altogether, our combined data allowed us to propose a model for W42R pathogenesis, with the W42R mutant serving as a mimic for photodamaged γD-crystallin involved in age-related cataract.
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Affiliation(s)
- Fangling Ji
- School of Life Science and Biotechnology, Dalian University of Technology, Lingong Road, Dalian 116024, China
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8
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Moreau KL, King JA. Protein misfolding and aggregation in cataract disease and prospects for prevention. Trends Mol Med 2012; 18:273-82. [PMID: 22520268 DOI: 10.1016/j.molmed.2012.03.005] [Citation(s) in RCA: 296] [Impact Index Per Article: 24.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Revised: 03/01/2012] [Accepted: 03/14/2012] [Indexed: 11/16/2022]
Abstract
The transparency of the eye lens depends on maintaining the native tertiary structures and solubility of the lens crystallin proteins over a lifetime. Cataract, the leading cause of blindness worldwide, is caused by protein aggregation within the protected lens environment. With age, covalent protein damage accumulates through pathways thought to include UV radiation, oxidation, deamidation, and truncations. Experiments suggest that the resulting protein destabilization leads to partially unfolded, aggregation-prone intermediates and the formation of insoluble, light-scattering protein aggregates. These aggregates either include or overwhelm the protein chaperone content of the lens. Here, we review the causes of cataract and nonsurgical methods being investigated to inhibit or delay cataract development, including natural product-based therapies, modulators of oxidation, and protein aggregation inhibitors.
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Affiliation(s)
- Kate L Moreau
- Massachusetts Institute of Technology, Department of Biology, 77 Massachusetts Avenue, 68-330, Cambridge, MA 02139, USA
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Li XQ, Cai HC, Zhou SY, Yang JH, Xi YB, Gao XB, Zhao WJ, Li P, Zhao GY, Tong Y, Bao FC, Ma Y, Wang S, Yan YB, Lu CL, Ma X. A novel mutation impairing the tertiary structure and stability of γC-crystallin (CRYGC) leads to cataract formation in humans and zebrafish lens. Hum Mutat 2011; 33:391-401. [DOI: 10.1002/humu.21648] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2011] [Accepted: 10/17/2011] [Indexed: 11/09/2022]
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10
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Song S, Liang JJN, Mulhern ML, Madson CJ, Shinohara T. Cholesterol-derived bile acids enhance the chaperone activity of α-crystallins. Cell Stress Chaperones 2011; 16:475-80. [PMID: 21380614 PMCID: PMC3156260 DOI: 10.1007/s12192-011-0259-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Revised: 02/09/2011] [Accepted: 02/10/2011] [Indexed: 02/05/2023] Open
Abstract
Human lens membranes contain the highest cholesterol concentration of any known biological membranes, but it significantly decreases with age. Oxygenation of cholesterol generates numerous forms of oxysterols (bile acids). We previously showed that two forms of the bile acid components--ursodeoxycholic acid (UDCA) and tauroursodeoxycholic acid (TUDCA)--suppressed lens epithelial cell death and alleviated cataract formation in galactosemic rat lenses. We investigated whether these compounds also suppress the thermal aggregation of human lens crystallins. Total water-soluble (WS) proteins were prepared from human lenses, and recombinant human crystallins (αA-, αB-, βB2-, and γC-crystallin) were generated by a prokaryotic expression system and purified by liquid chromatography. The light scattering of proteins in the presence or absence of UDCA or TUDCA was measured using a spectrofluorometer set at Ex/Em = 400/400 nm. Protein blot analysis was conducted for detection of α-crystallins in the human lens WS proteins. High concentrations of UDCA and TUDCA significantly suppressed thermal aggregation of total lens WS proteins, which contained a low level of αA-/αB-crystallin. Spectroscopic analysis with each recombinant human lens crystallin indicated that the bile acids did not suppress the thermal aggregation of γC-, βB2-, αA-, or αB-crystallin. Combination of α-crystallin and bile acid (either UDCA or TUDCA) suppressed thermal aggregation of each individual crystallin as well as a non-crystallin protein, insulin. These results suggest that UDCA or TUDCA protects the chaperone activity of α-crystallin. It is believed that these two naturally occurring intermediate waste products in the lens enhance the chaperone activity of α-crystallin. This finding may lead to the development of UDCA and TUDCA as anticataract agents.
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Affiliation(s)
- Shuhua Song
- Ophthalmic Research/Surgery, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA USA
| | - Jack J. N. Liang
- Ophthalmic Research/Surgery, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA USA
| | - Michael L. Mulhern
- Department of Ophthalmology and Visual Sciences, University of Nebraska Medical Center, Omaha, NE 68198-5840 USA
| | - Christian J. Madson
- Department of Ophthalmology and Visual Sciences, University of Nebraska Medical Center, Omaha, NE 68198-5840 USA
| | - Toshimichi Shinohara
- Department of Ophthalmology and Visual Sciences, University of Nebraska Medical Center, Omaha, NE 68198-5840 USA
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11
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Banerjee PR, Pande A, Patrosz J, Thurston GM, Pande J. Cataract-associated mutant E107A of human gammaD-crystallin shows increased attraction to alpha-crystallin and enhanced light scattering. Proc Natl Acad Sci U S A 2011; 108:574-9. [PMID: 21173272 PMCID: PMC3021023 DOI: 10.1073/pnas.1014653107] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Several point mutations in human γD-crystallin (HGD) are now known to be associated with cataract. So far, the in vitro studies of individual mutants of HGD alone have been sufficient in providing plausible molecular mechanisms for the associated cataract in vivo. Nearly all the mutant proteins in solution showed compromised solubility and enhanced light scattering due to altered homologous γ-γ crystallin interactions. In sharp contrast, here we present an intriguing case of a human nuclear cataract-associated mutant of HGD--namely Glu107 to Ala (E107A), which is nearly identical to the wild type in structure, stability, and solubility properties, with one exception: Its pI is higher by nearly one pH unit. This increase dramatically alters its interaction with α-crystallin. There is a striking difference in the liquid-liquid phase separation behavior of E107A-α-crystallin mixtures compared to HGD-α-crystallin mixtures, and the light-scattering intensities are significantly higher for the former. The data show that the two coexisting phases in the E107A-α mixtures differ much more in protein density than those that occur in HGD-α mixtures, as the proportion of α-crystallin approaches that in the lens nucleus. Thus in HGD-α mixtures, the demixing of phases occurs primarily by protein type while in E107A-α mixtures it is increasingly governed by protein density. Analysis of these results suggests that the cataract due to the E107A mutation could result from the instability caused by the altered attractive interactions between dissimilar proteins--i.e., heterologous γ-α crystallin interactions--primarily due to the change in surface electrostatic potential in the mutant protein.
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Affiliation(s)
| | | | - Julita Patrosz
- Department of Biology, University at Albany, State University of New York, Albany, NY 12222; and
| | - George M. Thurston
- Department of Physics, Rochester Institute of Technology, Rochester, NY 14623
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Huang B, He W. Molecular characteristics of inherited congenital cataracts. Eur J Med Genet 2010; 53:347-57. [PMID: 20624502 DOI: 10.1016/j.ejmg.2010.07.001] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2010] [Accepted: 07/04/2010] [Indexed: 01/20/2023]
Abstract
Congenital cataracts are a major cause of induced blindness in children, and inherited cataracts are the major cause of congenital cataracts. Inherited congenital cataracts have been associated with mutations in specific genes, including those of crystallins, gap junction proteins, membrane transport and channel proteins, the cytoskeleton, and growth and transcription factors. Locating and identifying the genes and mutations involved in cataractogenesis are essential to gaining an understanding of the molecular defects and pathophysiologic characteristics of inherited congenital cataracts. In this review, we summarize the current research in this field.
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Affiliation(s)
- Bingyu Huang
- Medical Genetics Laboratory, Department of Obstetrics and Gynecology, Second Teaching Hospital, Jilin University, 218 Zhiqiang, Changchun, 130041, China.
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A single destabilizing mutation (F9S) promotes concerted unfolding of an entire globular domain in gammaS-crystallin. J Mol Biol 2010; 399:320-30. [PMID: 20382156 DOI: 10.1016/j.jmb.2010.04.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2009] [Revised: 03/30/2010] [Accepted: 04/01/2010] [Indexed: 11/22/2022]
Abstract
Conformational change and aggregation of native proteins are associated with many serious age-related and neurological diseases. gammaS-Crystallin is a highly stable, abundant structural component of vertebrate eye lens. A single F9S mutation in the N-terminal domain of mouse gammaS-crystallin causes the severe Opj cataract, with disruption of cellular organization and appearance of fibrillar structures in the lens. Although the mutant protein has a near-native fold at room temperature, significant increases in hydrogen/deuterium exchange rates were observed by NMR for all the well-protected beta-sheet core residues throughout the entire N-terminal domain of the mutant protein, resulting in up to a 3.5-kcal/mol reduction in the free energy of the folding/unfolding equilibrium. No difference was detected for the C-terminal domain. At a higher temperature, this effect further increases to allow for a much more uniform exchange rate among the N-terminal core residues and those of the least well-structured surface loops. This suggests a concerted unfolding intermediate of the N-terminal domain, while the C-terminal domain stays intact. Increasing concentrations of guanidinium chloride produced two transitions for the Opj mutant, with an unfolding intermediate at approximately 1 M guanidinium chloride. The consequence of this partial unfolding, whether by elevated temperature or by denaturant, is the formation of thioflavin T staining aggregates, which demonstrated fibril-like morphology by atomic force microscopy. Seeding with the already unfolded protein enhanced the formation of fibrils. The Opj mutant protein provides a model for stress-related unfolding of an essentially normally folded protein and production of aggregates with some of the characteristics of amyloid fibrils.
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14
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Liu BF, Song S, Hanson M, Liang JJN. Protein-protein interactions involving congenital cataract T5P gammaC-crystallin mutant: a confocal fluorescence microscopy study. Exp Eye Res 2008; 87:515-20. [PMID: 18926820 DOI: 10.1016/j.exer.2008.08.021] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2008] [Revised: 07/14/2008] [Accepted: 08/14/2008] [Indexed: 11/28/2022]
Abstract
The human lens crystallin gene CRYGC T5P is associated with Coppock-like cataract and has a phenotype of a dust-like opacity of the fetal lens nucleus and deep cortical region. Previous in vitro mutation studies indicate that the protein has changed conformation, solubility, and stability, which may make it susceptible to aggregation, as seen in cataractous lens and cell culture expression. To investigate the mechanisms leading to these events, we studied protein-protein interactions using confocal fluorescence resonance energy transfer (FRET) microscopy. The method detects protein-protein interactions in the natural environment of living cells. Crystallin genes (CRYGC T5P, CRYGC, and CRYAA) were fused to either the green fluorescence protein (GFP) or red fluorescence protein (DsRED or RFP) vector. Each of the following GFP-RFP (donor-acceptor) plasmid pairs was cotransfected into HeLa cells: gammaC-gammaC, gammaC-gammaCT5P, gammaCT5P-gammaCT5P, alphaA-gammaC, and alphaA-gammaCT5P. After culture, confocal fluorescence cell images were taken. Protein-protein interactions in the form of net FRET were evaluated. The confocal fluorescence images show that cells expressing T5P gammaC-crystallin contain many protein aggregates, but cells co-expressing with either gammaC- or alphaA-crystallin reduce the aggregation considerably. FRET determination indicates that gammaCT5P-gammaCT5P shows less protein-protein interaction than either gammaC-gammaC or gammaC-gammaCT5P. Cotransfection with alphaA-crystallin (alphaA-gammaC or alphaA-T5PgammaC) increases nFRET compared with gammaC-gammaC or gammaC-T5PgammaC. Our results demonstrate that T5P gammaC-crystallin shows more protein aggregates and less protein-protein interaction than WT gammaC-crystallin. Chaperone alphaA-crystallin can rescue T5P gammaC-crystallin from aggregation through increased protein interaction. The formation of congenital cataract may be due to reduced protein-protein interactions and increased aggregation from an insufficient amount of alpha-crystallin for protection.
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Affiliation(s)
- Bing-Fen Liu
- Center for Ophthalmic Research, Brigham and Women's Hospital, Boston, MA 02115-5822, USA
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15
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Evans P, Bateman OA, Slingsby C, Wallace BA. A reference dataset for circular dichroism spectroscopy tailored for the βγ-crystallin lens proteins. Exp Eye Res 2007; 84:1001-8. [PMID: 17400211 DOI: 10.1016/j.exer.2007.01.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2006] [Revised: 01/12/2007] [Accepted: 01/16/2007] [Indexed: 11/24/2022]
Abstract
Circular dichroism (CD) spectroscopy is a powerful solution technique for the study of protein secondary structure. As hierarchical euclidean clustering analyses of high quality crystallin synchrotron radiation circular dichroism (SRCD) spectral data can be separated into structural groups based solely on spectral information, the technique can potentially be improved to more accurately determine secondary structures and monitor conformational changes in crystallins. Secondary structure estimates can be determined through use of reference datasets of circular dichroism spectra from proteins with determined crystal structures. As with any empirical method, the accuracies of the analyses are dependent upon how closely the reference dataset characteristics match those of the protein to be studied. To date, crystallin proteins have not been well analysed by CD because existing reference datasets do not contain good representations of their structural characteristics. This work describes a betagamma-crystallin specific reference dataset, CRYST175, which was created solely for the study of betagamma-crystallin secondary structures. Prediction accuracy was assessed for the new dataset using several deconvolution algorithms and it was found to substantially outperform existing more general reference datasets.
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Affiliation(s)
- P Evans
- Department of Crystallography, Birkbeck College, University of London, Malet Street, London, WC1E 7HX, UK
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16
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Xia CH, Cheng C, Huang Q, Cheung D, Li L, Dunia I, Benedetti LE, Horwitz J, Gong X. Absence of alpha3 (Cx46) and alpha8 (Cx50) connexins leads to cataracts by affecting lens inner fiber cells. Exp Eye Res 2006; 83:688-96. [PMID: 16696970 DOI: 10.1016/j.exer.2006.03.013] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2005] [Revised: 03/09/2006] [Accepted: 03/21/2006] [Indexed: 12/31/2022]
Abstract
Lens development and transparency have been hypothesized to depend on intercellular gap junction channels, consisting of alpha3 (Cx46) and alpha8 (Cx50) connexin subunits, to transport metabolites, secondary messages and ions between lens cells. To evaluate this hypothesis, we have generated alpha3(-/-) alpha8(-/-) double knockout mice and characterized their lens phenotypes. Without gap junctions between lens fiber cells, alpha3(-/-) alpha8(-/-) lenses displayed severe cataracts resulting from cell swelling and degeneration of inner fibers while normal peripheral fiber cells continued to form throughout life. Neither an increase of degraded crystallins nor an increase of water-insoluble crystallins was found in alpha3(-/-) alpha8(-/-) lenses. However, a substantial reduction of gamma-crystallin proteins, but not alpha- and beta-crystallins, was detected. These results suggest that gap junction communication is important for maintaining lens homeostasis of inner fiber cells and that a loss of gap junctions leads to cataract formation as well as reductions of gamma-crystallin proteins and transcripts.
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Affiliation(s)
- Chun-hong Xia
- School of Optometry and Vision Science Program, University of California at Berkeley, 693 Minor Hall, Berkeley, CA 94720-2020, USA
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Zetterberg M, Zhang X, Taylor A, Liu B, Liang JJ, Shang F. Glutathiolation enhances the degradation of gammaC-crystallin in lens and reticulocyte lysates, partially via the ubiquitin-proteasome pathway. Invest Ophthalmol Vis Sci 2006; 47:3467-73. [PMID: 16877417 PMCID: PMC2117893 DOI: 10.1167/iovs.05-1664] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE S-glutathiolated proteins are formed in the lens during aging and cataractogenesis. The objective of this work was to explore the role of the ubiquitin-proteasome pathway in eliminating S-glutathiolated gammaC-crystallin. METHODS Recombinant human gammaC-crystallin was mixed with various concentrations of glutathione (GSH) and diamide at 25 degrees C for 1 hour. The extent of glutathiolation of the gammaC-crystallin was determined by mass spectrometry. Native and S-glutathiolated gammaC-crystallins were labeled with (125)I, and proteolytic degradation was determined using both lens fiber lysate and reticulocyte lysate as sources of ubiquitinating and proteolytic enzymes. Far UV circular dichroism, tryptophan fluorescence intensity, and binding to the hydrophobic fluorescence probe 4,4'-dianilino-1,1'-binaphthalene-5,5'-disulfonic acid (Bis-ANS), were used to characterize the native and glutathiolated gammaC-crystallins. RESULTS On average, two and five of the eight cysteines in gammaC-crystallin were glutathiolated when molar ratios of gammaC-crystallin-GSH-diamide were 1:2:5 and 1:10:25, respectively. Native gammaC-crystallin was resistant to degradation in both lens fiber lysate and reticulocyte lysate. However, glutathiolated gammaC-crystallin showed a significant increase in proteolytic degradation in both lens fiber and reticulocyte lysates. Proteolysis was stimulated by addition of adenosine triphosphate (ATP) and Ubc4 and was substantially inhibited by the proteasome inhibitor MG132 and a dominant negative form of ubiquitin, indicating that at least part of the proteolysis was mediated by the ubiquitin-proteasome pathway. Spectroscopic analyses of glutathiolated gammaC-crystallin revealed conformational changes and partial unfolding, which may provide a signal for the ubiquitin-dependent degradation. CONCLUSIONS The present data demonstrate that oxidative modification by glutathiolation can render lens proteins more susceptible to degradation by the ubiquitin-proteasome pathway. Together with previous results, these data support the concept that the ubiquitin-proteasome pathway serves as a general protein quality-control mechanism.
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Affiliation(s)
- Madeleine Zetterberg
- Laboratory for Nutrition and Vision Research, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts
- Department of Ophthalmology, Institute of Clinical Neuroscience, University of Göteborg, Sweden
- Institute of Anatomy and Cell Biology, University of Göteborg, Sweden
| | - Xinyu Zhang
- Laboratory for Nutrition and Vision Research, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts
| | - Allen Taylor
- Laboratory for Nutrition and Vision Research, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts
| | - Bingfen Liu
- Ophthalmic Research Center, Brigham and Womens’s Hospital, Harvard Medical School, Boston, Massachusetts
| | - Jack J. Liang
- Ophthalmic Research Center, Brigham and Womens’s Hospital, Harvard Medical School, Boston, Massachusetts
| | - Fu Shang
- Laboratory for Nutrition and Vision Research, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts
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18
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Flaugh SL, Mills IA, King J. Glutamine deamidation destabilizes human gammaD-crystallin and lowers the kinetic barrier to unfolding. J Biol Chem 2006; 281:30782-93. [PMID: 16891314 DOI: 10.1074/jbc.m603882200] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human eye lens transparency requires life long stability and solubility of the crystallin proteins. Aged crystallins have high levels of covalent damage, including glutamine deamidation. Human gammaD-crystallin (HgammaD-Crys) is a two-domain beta-sheet protein of the lens nucleus. The two domains interact through interdomain side chain contacts, including Gln-54 and Gln-143, which are critical for stability and folding of the N-terminal domain of HgammaD-Crys. To test the effects of interface deamidation on stability and folding, single and double glutamine to glutamate substitutions were constructed. Equilibrium unfolding/refolding experiments of the proteins were performed in guanidine hydrochloride at pH 7.0, 37 degrees C, or urea at pH 3.0, 20 degrees C. Compared with wild type, the deamidation mutants were destabilized at pH 7.0. The proteins populated a partially unfolded intermediate that likely had a structured C-terminal domain and unstructured N-terminal domain. However, at pH 3.0, equilibrium unfolding transitions of wild type and the deamidation mutants were indistinguishable. In contrast, the double alanine mutant Q54A/Q143A was destabilized at both pH 7.0 and 3.0. Thermal stabilities of the deamidation mutants were also reduced at pH 7.0. Similarly, the deamidation mutants lowered the kinetic barrier to unfolding of the N-terminal domain. These data indicate that interface deamidation decreases the thermodynamic stability of HgammaD-Crys and lowers the kinetic barrier to unfolding due to introduction of a negative charge into the domain interface. Such effects may be significant for cataract formation by inducing protein aggregation or insolubility.
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Affiliation(s)
- Shannon L Flaugh
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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19
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Liang JJ, Liu BF. Fluorescence resonance energy transfer study of subunit exchange in human lens crystallins and congenital cataract crystallin mutants. Protein Sci 2006; 15:1619-27. [PMID: 16751613 PMCID: PMC2242568 DOI: 10.1110/ps.062216006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Lens alpha-crystallin is an oligomeric protein with a molecular mass of 500-1000 kDa and a polydispersed assembly. It consists of two types of subunits, alphaA and alphaB, each with a molecular mass of 20 kDa. The subunits also form homo-oligomers in some other tissues and in vitro. Their quaternary structures, which are dynamic and characterized by subunit exchange, have been studied by many techniques, including fluorescence resonance energy transfer (FRET) and mass spectrometry analysis. The proposed mechanism of subunit exchange has been either by dissociation/association of monomeric subunits or by rapid equilibrium between oligomers and suboligomers. To explore the nature of subunit exchange further, we performed additional FRET measurements and analyses using a fluorescent dye-labeled W9F alphaA-crystallin as the acceptor probe and Trp in other crystallins (wild-type and R116C alphaA, wild-type and R120G alphaB, wild-type and Q155* betaB2) as the donor probe and calculated the transfer efficiency, Förster distance, and average distance between two probes. The results indicate only slight decreased efficiency and increased distance between two probes for the R116C alphaA and R120G alphaB mutations despite conformational changes.
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Affiliation(s)
- Jack J Liang
- Ophthalmic Research/Surgery, Brigham and Women's Hospital, Department of Ophthalmology, Harvard Medical School, Boston, MA 02115, USA.
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20
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Flaugh SL, Kosinski-Collins MS, King J. Interdomain side-chain interactions in human gammaD crystallin influencing folding and stability. Protein Sci 2005; 14:2030-43. [PMID: 16046626 PMCID: PMC2279314 DOI: 10.1110/ps.051460505] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Human gammaD crystallin (HgammaD-Crys) is a two domain, beta-sheet eye lens protein that must remain soluble throughout life for lens transparency. Single amino acid substitutions of HgammaD-Crys are associated with juvenile-onset cataracts. Features of the interface between the two domains conserved among gamma-crystallins are a central six-residue hydrophobic cluster, and two pairs of interacting residues flanking the cluster. In HgammaD-Crys these pairs are Gln54/Gln143 and Arg79/Met147. We previously reported contributions of the hydrophobic cluster residues to protein stability. In this study alanine substitutions of the flanking residue pairs were constructed and analyzed. Equilibrium unfolding/refolding experiments at 37 degrees C revealed a plateau in the unfolding/refolding transitions, suggesting population of a partially folded intermediate with a folded C-terminal domain (C-td) and unfolded N-terminal domain (N-td). The N-td was destabilized by substituting residues from both domains. In contrast, the C-td was not significantly affected by substitutions of either domain. Refolding rates of the N-td were significantly decreased for mutants of either domain. In contrast, refolding rates of the C-td were similar to wild type for mutants of either domain. Therefore, domain interface residues of the folded C-td probably nucleate refolding of the N-td. We suggest that these residues stabilize the native state by shielding the central hydrophobic cluster from solvent. Glutamine and methionine side chains are among the residues covalently damaged in aged and cataractous lenses. Such damage may generate partially unfolded, aggregation- prone conformations of HgammaD-Crys that could be significant in cataract.
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Affiliation(s)
- Shannon L Flaugh
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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21
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Liang JJN. Interactions and chaperone function of alphaA-crystallin with T5P gammaC-crystallin mutant. Protein Sci 2005; 13:2476-82. [PMID: 15322286 PMCID: PMC2280011 DOI: 10.1110/ps.04815104] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
T5P gammaC-crystallin mutation is associated with Coppock-like cataract, one of the autosomal dominant congenital cataracts. It is not known why the abundant alpha-crystallin cannot prevent the mutation-related aggregation. Our previous studies indicate that the mutation changes conformation and reduces solubility and stability, but it is not known whether it is these events or the loss of interaction with other crystallins that causes the cataract. It is also not known whether the alpha-crystallin can protect T5P mutant as effectively from heat-induced aggregation as the wild-type (WT) gammaC-crystallin. To investigate the mechanism of interactions and chaperone function between alphaA- and gammaC-crystallin, human alphaA-crystallin and W9F mutant as well as WT gammaC-crystallin and T5P mutant were cloned. Interactions between alphaA- and gammaC-crystallin were studied with fluorescence resonance energy transfer (FRET), and chaperone activity was assessed by the suppression of heat-induced aggregation of substrate proteins. Conformational changes of substrate proteins were studied by spectroscopic measurements. The results indicate that the T5P mutant showed a slightly greater FRET than WT gammaC-crystallin with alphaA-crystallin, and alphaA-crystallin could effectively prevent both WT and T5P gammaC-crystallin from heat-induced aggregation. Spectroscopic measurements show that both alphaA-crystallin and gammaC-crystallin underwent only slight conformational change after chaperone binding. Together with previous results obtained with a two-hybrid system assay of interactions between alphaA- and gammaC-crystallin, the present FRET and chaperone results indicate that loss of interactions of T5P mutant with other crystallins may play a larger role than the protection afforded by chaperone-like activity in Coppock-like cataract.
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Affiliation(s)
- Jack J-N Liang
- Center for Ophthalmic Research, Brigham and Women's Hospital, 221 Longwood Avenue, Boston, MA 02115, USA.
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22
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Evans P, Wyatt K, Wistow GJ, Bateman OA, Wallace BA, Slingsby C. The P23T Cataract Mutation Causes Loss of Solubility of Folded γD-Crystallin. J Mol Biol 2004; 343:435-44. [PMID: 15451671 DOI: 10.1016/j.jmb.2004.08.050] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2004] [Revised: 06/02/2004] [Accepted: 08/10/2004] [Indexed: 11/17/2022]
Abstract
Mutations in the human gammaD-crystallin gene have been linked to several types of congenital cataracts. In particular, the Pro23 to Thr (P23T) mutation of human gammaD crystallin has been linked to cerulean, lamellar, coralliform, and fasciculiform congenital cataracts. We have expressed and purified wild-type human gammaD, P23T, and the Pro23 to Ser23 (P23S) mutant. Our measurements show that P23T is significantly less soluble than wild-type human gammaD, with P23S having an intermediate solubility. Using synchrotron radiation circular dichroism spectroscopy, we have determined that the P23T mutant has a slightly increased content of beta-sheet, which may be attributed to the extension of an edge beta-strand due to the substitution of Pro23 with a residue able to form hydrogen bonds. Neither of the point mutations appears to have reduced the thermal stability of the protein significantly, nor its resistance to guanidine hydrochloride-induced unfolding. These results suggest that insolubility, rather than loss of stability, is the primary basis for P23T congenital cataracts.
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Affiliation(s)
- P Evans
- Department of Crystallography, Birkbeck College, Malet Street, London WC1E 7HX, UK
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23
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Meehan S, Berry Y, Luisi B, Dobson CM, Carver JA, MacPhee CE. Amyloid Fibril Formation by Lens Crystallin Proteins and Its Implications for Cataract Formation. J Biol Chem 2004; 279:3413-9. [PMID: 14615485 DOI: 10.1074/jbc.m308203200] [Citation(s) in RCA: 145] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The alpha-, beta-, and gamma-crystallins are the major structural proteins within the eye lens and are responsible for its exceptional stability and transparency. Under mildly denaturing conditions, all three types of bovine crystallin assemble into fibrillar structures in vitro. Characterization by transmission electron microscopy, dye binding assays, and x-ray fiber diffraction shows that these species have all of the characteristics of fibrils associated with the family of amyloid diseases. Moreover, the full-length proteins are incorporated into the fibrils, (i.e. no protein cleavage is required for these species to form), although for the gamma-crystallins some fragmentation occurs under the conditions employed in this study. Our findings indicate that the inherent stability of the beta-sheet supramolecular structure adopted by the crystallins in the eye lens and the chaperone ability of alpha-crystallin must be crucial for preventing fibril formation in vivo. The crystallins are very stable proteins but undergo extensive post-translational modification with age that leads to their destabilization. The ability of the crystallins to convert into fibrils under destabilizing conditions suggests that this process could contribute to the development of cataract with aging.
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Affiliation(s)
- Sarah Meehan
- Biological Physics Group, Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE, United Kingdom
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24
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Nandrot E, Slingsby C, Basak A, Cherif-Chefchaouni M, Benazzouz B, Hajaji Y, Boutayeb S, Gribouval O, Arbogast L, Berraho A, Abitbol M, Hilal L. Gamma-D crystallin gene (CRYGD) mutation causes autosomal dominant congenital cerulean cataracts. J Med Genet 2003; 40:262-7. [PMID: 12676897 PMCID: PMC1735438 DOI: 10.1136/jmg.40.4.262] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Congenital cataracts are a major cause of bilateral visual impairment in childhood. We mapped the gene responsible for autosomal congenital cerulean cataracts to chromosome 2q33-35 in a four generation family of Moroccan descent. The maximum lod score (7.19 at recombination fraction theta=0) was obtained for marker D2S2208 near the gamma-crystallin gene (CRYG) cluster. Sequencing of the coding regions of the CRYGA, B, C, and D genes showed the presence of a heterozygous C>A transversion in exon 2 of CRYGD that is associated with cataracts in this family. This mutation resulted in a proline to threonine substitution at amino acid 23 of the protein in the first of the four Greek key motifs that characterise this protein. We show that although the x ray crystallography modelling does not indicate any change of the backbone conformation, the mutation affects a region of the Greek key motif that is important for determining the topology of this protein fold. Our data suggest strongly that the proline to threonine substitution may alter the protein folding or decrease the thermodynamic stability or solubility of the protein. Furthermore, this is the first report of a mutation in this gene resulting in autosomal dominant congenital cerulean cataracts.
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Affiliation(s)
- E Nandrot
- Centre de Recherches Thérapeutiques en Ophtalmologie de la Faculté de Médecine Necker, EA No 2502 du Ministére de la Recherche et de l'Enseignement Supérieur, Université René Descartes, Paris, France
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25
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Abstract
betaB2- and gammaC-crystallins belong to the betagamma-crystallin superfamily and have very similar structures. Molecular spectroscopic techniques such as UV-visible absorption, circular dichroism, and fluorescence indicate they have similar biophysical properties. Their structures are characterized by the presence of two domains consisting of four Greek key motifs. The only difference is the connecting peptide of the two domains, which is flexible in gamma-crystallin but extended in beta-crystallin; thus, an intradomain association and a monomer are formed in gamma-crystallin and an interdomain association and a dimer are formed in beta-crystallin. The difference may be reflected in the thermodynamic stability. In the present study, we calculated the standard free-energy by equilibrium unfolding transition in guanidine hydrochloride using three spectroscopic parameters: absorbance at 235nm, Trp fluorescence intensity at 320nm, and far-UV circular dichroism at 223nm. Global analyses indicate that both dimeric betaB2- and monomeric gammaC-crystallins are a better fit to a three-state model than to a two-state model. In terms of standard free-energy, deltaG(0)(H(2)O,i) both betaB2-crystallin and gammaC-crystallin are stable proteins and dimeric betaB2-crystallin is more stable than the monomeric gammaC-crystallin. The significance of the thermodynamic stability for betaB2- and gammaC-crystallins may be related to their functions in the lens.
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Affiliation(s)
- Ling Fu
- Department of Ophthalmology, Center for Ophthalmic Research, Brigham and Women's Hospital, Harvard Medical School, 221 Longwood Avenue, Boston, MA 02115, USA
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