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Cvekl A, Vijg J. Aging of the eye: Lessons from cataracts and age-related macular degeneration. Ageing Res Rev 2024; 99:102407. [PMID: 38977082 DOI: 10.1016/j.arr.2024.102407] [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: 03/11/2024] [Revised: 06/18/2024] [Accepted: 07/01/2024] [Indexed: 07/10/2024]
Abstract
Aging is the greatest risk factor for chronic human diseases, including many eye diseases. Geroscience aims to understand the effects of the aging process on these diseases, including the genetic, molecular, and cellular mechanisms that underlie the increased risk of disease over the lifetime. Understanding of the aging eye increases general knowledge of the cellular physiology impacted by aging processes at various biological extremes. Two major diseases, age-related cataract and age-related macular degeneration (AMD) are caused by dysfunction of the lens and retina, respectively. Lens transparency and light refraction are mediated by lens fiber cells lacking nuclei and other organelles, which provides a unique opportunity to study a single aging hallmark, i.e., loss of proteostasis, within an environment of limited metabolism. In AMD, local dysfunction of the photoreceptors/retinal pigmented epithelium/Bruch's membrane/choriocapillaris complex in the macula leads to the loss of photoreceptors and eventually loss of central vision, and is driven by nearly all the hallmarks of aging and shares features with Alzheimer's disease, Parkinson's disease, cardiovascular disease, and diabetes. The aging eye can function as a model for studying basic mechanisms of aging and, vice versa, well-defined hallmarks of aging can be used as tools to understand age-related eye disease.
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Affiliation(s)
- Ales Cvekl
- Departments of Genetics and Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| | - Jan Vijg
- Departments of Genetics and Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
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2
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Serebryany E, Martin RW, Takahashi GR. The Functional Significance of High Cysteine Content in Eye Lens γ-Crystallins. Biomolecules 2024; 14:594. [PMID: 38786000 PMCID: PMC11118217 DOI: 10.3390/biom14050594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2024] [Revised: 05/07/2024] [Accepted: 05/14/2024] [Indexed: 05/25/2024] Open
Abstract
Cataract disease is strongly associated with progressively accumulating oxidative damage to the extremely long-lived crystallin proteins of the lens. Cysteine oxidation affects crystallin folding, interactions, and light-scattering aggregation especially strongly due to the formation of disulfide bridges. Minimizing crystallin aggregation is crucial for lifelong lens transparency, so one might expect the ubiquitous lens crystallin superfamilies (α and βγ) to contain little cysteine. Yet, the Cys content of γ-crystallins is well above the average for human proteins. We review literature relevant to this longstanding puzzle and take advantage of expanding genomic databases and improved machine learning tools for protein structure prediction to investigate it further. We observe remarkably low Cys conservation in the βγ-crystallin superfamily; however, in γ-crystallin, the spatial positioning of Cys residues is clearly fine-tuned by evolution. We propose that the requirements of long-term lens transparency and high lens optical power impose competing evolutionary pressures on lens βγ-crystallins, leading to distinct adaptations: high Cys content in γ-crystallins but low in βB-crystallins. Aquatic species need more powerful lenses than terrestrial ones, which explains the high methionine content of many fish γ- (and even β-) crystallins. Finally, we discuss synergies between sulfur-containing and aromatic residues in crystallins and suggest future experimental directions.
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Affiliation(s)
- Eugene Serebryany
- Department of Physiology & Biophysics, Stony Brook University, SUNY, Stony Brook, NY 11794, USA
- Laufer Center for Physical & Quantitative Biology, Stony Brook University, SUNY, Stony Brook, NY 11794, USA
| | - Rachel W. Martin
- Department of Chemistry, UCI Irvine, Irvine, CA 92697-2025, USA
- Department of Molecular Biology & Biochemistry, UCI Irvine, Irvine, CA 92697-3900, USA
| | - Gemma R. Takahashi
- Department of Molecular Biology & Biochemistry, UCI Irvine, Irvine, CA 92697-3900, USA
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3
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Bergman MR, Hernandez SA, Deffler C, Yeo J, Deravi LF. Design and Characterization of Model Systems that Promote and Disrupt Transparency of Vertebrate Crystallins In Vitro. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2303279. [PMID: 37897315 PMCID: PMC10724405 DOI: 10.1002/advs.202303279] [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] [Received: 05/20/2023] [Revised: 08/31/2023] [Indexed: 10/30/2023]
Abstract
Positioned within the eye, the lens supports vision by transmitting and focusing light onto the retina. As an adaptive glassy material, the lens is constituted primarily by densely-packed, polydisperse crystallin proteins that organize to resist aggregation and crystallization at high volume fractions, yet the details of how crystallins coordinate with one another to template and maintain this transparent microstructure remain unclear. The role of individual crystallin subtypes (α, β, and γ) and paired subtype compositions, including how they experience and resist crowding-induced turbidity in solution, is explored using combinations of spectrophotometry, hard-sphere simulations, and surface pressure measurements. After assaying crystallin combinations, β-crystallins emerged as a principal component in all mixtures that enabled dense fluid-like packing and short-range order necessary for transparency. These findings helped inform the design of lens-like hydrogel systems, which are used to monitor and manipulate the loss of transparency under different crowding conditions. When taken together, the findings illustrate the design and characterization of adaptive materials made from lens proteins that can be used to better understand mechanisms regulating transparency.
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Affiliation(s)
- Michael R. Bergman
- Department of Chemistry and Chemical BiologyNortheastern University360 Huntington AveBostonMA02115USA
| | - Sophia A. Hernandez
- Department of Chemistry and Chemical BiologyNortheastern University360 Huntington AveBostonMA02115USA
| | - Caitlin Deffler
- Department of Chemistry and Chemical BiologyNortheastern University360 Huntington AveBostonMA02115USA
| | - Jingjie Yeo
- Sibley School of Mechanical and Aerospace EngineeringCornell University413 Upson Hall, 124 Hoy RdIthacaNY14850USA
| | - Leila F. Deravi
- Department of Chemistry and Chemical BiologyNortheastern University360 Huntington AveBostonMA02115USA
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Zhu S, Xi Y, Xu J, Hu L, Luo C, Yao K, Chen X. The 18th amino acid glycine plays an essential role in maintaining the structural stabilities of γS-crystallin linking with congenital cataract. Int J Biol Macromol 2023; 251:126339. [PMID: 37586630 DOI: 10.1016/j.ijbiomac.2023.126339] [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: 03/31/2023] [Revised: 08/11/2023] [Accepted: 08/12/2023] [Indexed: 08/18/2023]
Abstract
γS-crystallin is particularly rich in the embryonic nuclear region and is crucial to the maintenance of lens transparency and optical properties. Gene mutations in crystallin are the main factors leading to congenital hereditary cataracts, which are a major cause of visual impairment in children. Some mutations located in the 18th amino acid glycine of γS-crystallin were reported to be linking with congenital cataracts. However, the pathogenic mechanism has not been elucidated. Interestingly, we previously identified a novel variant of γS-crystallin (c.53G > A; p. G18D) with progressive cortical and sutural congenital cataracts in one Chinese family. In this study, we purified the γS-crystallin wildtype and mutant proteins to investigate the effects of the G18D mutation on the structural stability of γS-crystallin. The results showed that there were tertiary structural differences between the wild-type γS-crystallin and the G18D variant. The mutation significantly impaired the stability of γS-crystallin under environmental stress and promoted aggregation. Furthermore, molecular dynamics (MD) simulations showed that the mutation altered H-bonding and surface electrostatic potential. Significantly decreased stability along with an increased tendency to aggregate under environmental stress may be the major pathogenic factors for cataracts induced by the G18D mutation.
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Affiliation(s)
- Sha Zhu
- Eye Center, The Second Affiliated Hospital, School of Medicine, Zhejiang University, Zhejiang Provincial Key Laboratory of Ophthalmology, Zhejiang Provincial Clinical Research Center for Eye Diseases, Zhejiang Provincial Engineering Institute on Eye Diseases, Hangzhou 310009, Zhejiang, China
| | - Yibo Xi
- State Key Laboratory of Membrane Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Jingjie Xu
- Eye Center, The Second Affiliated Hospital, School of Medicine, Zhejiang University, Zhejiang Provincial Key Laboratory of Ophthalmology, Zhejiang Provincial Clinical Research Center for Eye Diseases, Zhejiang Provincial Engineering Institute on Eye Diseases, Hangzhou 310009, Zhejiang, China
| | - Lidan Hu
- State Key Laboratory of Membrane Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China; The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou 310052, China
| | - Chenqi Luo
- Eye Center, The Second Affiliated Hospital, School of Medicine, Zhejiang University, Zhejiang Provincial Key Laboratory of Ophthalmology, Zhejiang Provincial Clinical Research Center for Eye Diseases, Zhejiang Provincial Engineering Institute on Eye Diseases, Hangzhou 310009, Zhejiang, China
| | - Ke Yao
- Eye Center, The Second Affiliated Hospital, School of Medicine, Zhejiang University, Zhejiang Provincial Key Laboratory of Ophthalmology, Zhejiang Provincial Clinical Research Center for Eye Diseases, Zhejiang Provincial Engineering Institute on Eye Diseases, Hangzhou 310009, Zhejiang, China.
| | - Xiangjun Chen
- Eye Center, The Second Affiliated Hospital, School of Medicine, Zhejiang University, Zhejiang Provincial Key Laboratory of Ophthalmology, Zhejiang Provincial Clinical Research Center for Eye Diseases, Zhejiang Provincial Engineering Institute on Eye Diseases, Hangzhou 310009, Zhejiang, China; Institute of Translational Medicine, Zhejiang University School of Medicine, 268 Kaixuan Road, Hangzhou 310020, China.
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5
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Tanouye FT, Alves JR, Spinozzi F, Itri R. Unveiling protein-protein interaction potential through Monte Carlo simulation combined with small-angle X-ray scattering. Int J Biol Macromol 2023; 248:125869. [PMID: 37473888 DOI: 10.1016/j.ijbiomac.2023.125869] [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: 03/03/2023] [Revised: 07/06/2023] [Accepted: 07/15/2023] [Indexed: 07/22/2023]
Abstract
Protein interactions are investigated under different conditions of lysozyme concentration, temperature and ionic strength by means of in-solution small angle X-Ray scattering (SAXS) experiments and Monte Carlo (MC) simulations. Initially, experimental data were analysed through a Hard-Sphere Double Yukawa (HSDY) model combined with Random Phase Approximation (RPA), a closure relationship commonly used in the literature for monodisperse systems. We realized by means of MC that the HSDY/RPA modelling fails to describe the protein-protein pair potential for moderated and dense systems at low ionic strength, mainly due to inherent distortions of the RPA approximation. Our SAXS/MC results thus show that lysozyme concentrations between 2 (diluted) and 20 mg/mL (not crowded) present similar protein-protein pair potential preserving the values of surface net charge around 7 e, protein diameter of 28 Å, decay range of attractive well potential of 3 Å and a depth of the well potential varying from 1 to 5 kBT depending on temperature and salt addition. Noteworthy, we here propose a novel method to analyse the SAXS data from interacting proteins through MC simulations, which overcomes the deficiencies presented by the use of a closure relationship. Furthermore, this new methodology of combining SAXS with MC simulations gives a step forward to investigate more complex systems as those composed of a mixture of proteins of distinct species presenting different molecular weights (and hence sizes) and surface net charges at low, moderate and very dense systems.
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Affiliation(s)
| | | | - Francesco Spinozzi
- Department of Life and Environmental Sciences, Polytechnic University of Marche, Italy
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Pan X, Muir ER, Sellitto C, Wang K, Cheng C, Pierscionek B, Donaldson PJ, White TW. Age-Dependent Changes in the Water Content and Optical Power of the In Vivo Mouse Lens Revealed by Multi-Parametric MRI and Optical Modeling. Invest Ophthalmol Vis Sci 2023; 64:24. [PMID: 37079314 PMCID: PMC10132318 DOI: 10.1167/iovs.64.4.24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Accepted: 03/31/2023] [Indexed: 04/21/2023] Open
Abstract
Purpose The purpose of this study was to utilize in vivo magnetic resonance imaging (MRI) and optical modeling to investigate how changes in water transport, lens curvature, and gradient refractive index (GRIN) alter the power of the mouse lens as a function of age. Methods Lenses of male C57BL/6 wild-type mice aged between 3 weeks and 12 months (N = 4 mice per age group) were imaged using a 7T MRI scanner. Measurements of lens shape and the distribution of T2 (water-bound protein ratios) and T1 (free water content) values were extracted from MRI images. T2 values were converted into the refractive index (n) using an age-corrected calibration equation to calculate the GRIN at different ages. GRIN maps and shape parameters were inputted into an optical model to determine ageing effects on lens power and spherical aberration. Results The mouse lens showed two growth phases. From 3 weeks to 3 months, T2 decreased, GRIN increased, and T1 decreased. This was accompanied by increased lens thickness, volume, and surface radii of curvatures. The refractive power of the lens also increased significantly, and a negative spherical aberration was developed and maintained. Between 6 and 12 months of age, all physiological, geometrical, and optical parameters remained constant, although the lens continued to grow. Conclusions In the first 3 months, the mouse lens power increased as a result of changes in shape and in the GRIN, the latter driven by the decreased water content of the lens nucleus. Further research into the mechanisms regulating this decrease in mouse lens water could improve our understanding of how lens power changes during emmetropization in the developing human lens.
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Affiliation(s)
- Xingzheng Pan
- Department of Physiology, School of Medical Sciences, New Zealand Eye Centre, University of Auckland, New Zealand
| | - Eric R. Muir
- Department of Radiology, School of Medicine, Stony Brook University, Stony Brook, New York, United States
| | - Caterina Sellitto
- Department of Physiology & Biophysics, School of Medicine, Stony Brook University, Stony Brook, New York, United States
| | - Kehao Wang
- Beijing Advanced Innovation Centre for Biomedical Engineering, Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Engineering Medicine, Beihang University, Beijing, China
| | - Catherine Cheng
- School of Optometry and Vision Science Program, Indiana University, Bloomington, Indiana, United States
| | - Barbara Pierscionek
- Faculty of Health, Education, Medicine and Social Care, Medical Technology Research Centre, Anglia Ruskin University, Chelmsford Campus, United Kingdom
| | - Paul J. Donaldson
- Department of Physiology, School of Medical Sciences, New Zealand Eye Centre, University of Auckland, New Zealand
| | - Thomas W. White
- Department of Physiology & Biophysics, School of Medicine, Stony Brook University, Stony Brook, New York, United States
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7
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Velasco-Bolom JL, Dominguez L. Conformational stability of the deamidated and mutated human βB2-crystallin. Biophys Chem 2023; 296:106986. [PMID: 36905841 DOI: 10.1016/j.bpc.2023.106986] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 02/13/2023] [Accepted: 02/23/2023] [Indexed: 03/02/2023]
Abstract
Previous studies propose that genetic mutations and post-translational modifications in protein crystallins promote protein aggregation and are considered significant risk factors for cataract formation. The βB2-crystallin (HβB2C) forms a high proportion of proteins in the human eye lens. Different congenital mutations and post-translational deamidations in βB2-crystallin have been reported and linked to cataract formation. In this work, we employed extensive all-atom molecular dynamics simulations to evaluate the conformational stability of deamidated and mutated HβB2C. Our results show critical changes in the protein surface and its native contacts due to a modification in the conformational equilibrium of these proteins. The double deamidated (Q70E/Q162E) and single deamidated (Q70E) impact the well compact conformation of the HβB2C. These post-translational modifications allow the exposure of the protein hydrophobic interface, which lead to the exposure of electronegative residues. On the other hand, our mutational studies showed that the S143F mutation modifies the hydrogen-bond network of an antiparallel β-sheet, unfolding the C-terminal domain. Interestingly, the chain termination mutation (Q155X) does not unfold the N-terminal domain. However, the resultant conformation is more compact and avoids the exposure of the hydrophobic interface. Our results provide valuable information about the first steps of HβB2C unfolding in the presence of deamidated amino acids that have been reported to appear during aging. The findings reported in this work are essential for the general knowledge of the initial steps in the cataract formation mechanism, which may be helpful for the further development of molecules with pharmacological potential against cataract disease.
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Affiliation(s)
- José-Luis Velasco-Bolom
- Facultad de Química, Departamento de Fisicoquímica, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico
| | - Laura Dominguez
- Facultad de Química, Departamento de Fisicoquímica, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico.
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8
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Abstract
Purpose: Presbyopia-the progressive loss of near focus with age-is primarily a result of changes in lens biomechanics. In particular, the shape of the ocular lens in the absence of zonular tension changes significantly throughout adulthood. Contributors to this change in shape are changes in lens biomechanical properties, continuous volumetric growth lens, and possibly remodeling of the lens capsule. Knowledge in this area is growing rapidly, so the purpose of this mini-review was to summarize and synthesize these gains.Methods: We review the recent literature in this field.Results: The mechanisms governing age-related changes in biomechanical properties remains unknown. We have recently shown that lens growth may be driven by zonular tension. The same mechanobiological mechanism driving lens growth may also lead to remodeling of the capsule, though this remains to be demonstrated.Conclusions: This mini-review focuses on identifying mechanisms which cause these age-related changes, suggesting future work which may elucidate these mechanisms, and briefly discusses ongoing efforts to develop a non-surgical approach for therapeutic management of presbyopia. We also propose a simple model linking lens growth and biomechanical properties.
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Affiliation(s)
- Wade Rich
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
| | - Matthew A Reilly
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA.,Department of Ophthalmology & Visual Sciences, The Ohio State University, Columbus, OH, USA
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9
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Shu DY, Chaudhary S, Cho KS, Lennikov A, Miller WP, Thorn DC, Yang M, McKay TB. Role of Oxidative Stress in Ocular Diseases: A Balancing Act. Metabolites 2023; 13:187. [PMID: 36837806 PMCID: PMC9960073 DOI: 10.3390/metabo13020187] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Revised: 01/22/2023] [Accepted: 01/24/2023] [Indexed: 01/31/2023] Open
Abstract
Redox homeostasis is a delicate balancing act of maintaining appropriate levels of antioxidant defense mechanisms and reactive oxidizing oxygen and nitrogen species. Any disruption of this balance leads to oxidative stress, which is a key pathogenic factor in several ocular diseases. In this review, we present the current evidence for oxidative stress and mitochondrial dysfunction in conditions affecting both the anterior segment (e.g., dry eye disease, keratoconus, cataract) and posterior segment (age-related macular degeneration, proliferative vitreoretinopathy, diabetic retinopathy, glaucoma) of the human eye. We posit that further development of therapeutic interventions to promote pro-regenerative responses and maintenance of the redox balance may delay or prevent the progression of these major ocular pathologies. Continued efforts in this field will not only yield a better understanding of the molecular mechanisms underlying the pathogenesis of ocular diseases but also enable the identification of novel druggable redox targets and antioxidant therapies.
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Affiliation(s)
- Daisy Y. Shu
- Department of Ophthalmology, Schepens Eye Research Institute of Mass Eye and Ear, Harvard Medical School, Boston, MA 02114, USA
| | - Suman Chaudhary
- Department of Ophthalmology, Schepens Eye Research Institute of Mass Eye and Ear, Harvard Medical School, Boston, MA 02114, USA
| | - Kin-Sang Cho
- Department of Ophthalmology, Schepens Eye Research Institute of Mass Eye and Ear, Harvard Medical School, Boston, MA 02114, USA
| | - Anton Lennikov
- Department of Ophthalmology, Schepens Eye Research Institute of Mass Eye and Ear, Harvard Medical School, Boston, MA 02114, USA
| | - William P. Miller
- Department of Ophthalmology, Schepens Eye Research Institute of Mass Eye and Ear, Harvard Medical School, Boston, MA 02114, USA
| | - David C. Thorn
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA
| | - Menglu Yang
- Department of Ophthalmology, Schepens Eye Research Institute of Mass Eye and Ear, Harvard Medical School, Boston, MA 02114, USA
| | - Tina B. McKay
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
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10
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Regulation of lens water content: Effects on the physiological optics of the lens. Prog Retin Eye Res 2022:101152. [DOI: 10.1016/j.preteyeres.2022.101152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 11/21/2022] [Accepted: 11/22/2022] [Indexed: 12/09/2022]
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11
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Kapitunova AI, Dominova IN, Zhukov VV. γM Crystallin Genes in the Eye Lens of a Juvenile Common Carp Cyprinus carpio: Transcription Levels and Phylogenetic Aspect. J EVOL BIOCHEM PHYS+ 2022. [DOI: 10.1134/s0022093022040081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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12
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Xu W, Xu J, Shi C, Wu J, Wang H, Wu W, Chen X, Hu L. A novel cataract-causing mutation Ile82Met of γA crystallin trends to aggregate with unfolding intermediate. Int J Biol Macromol 2022; 211:357-367. [PMID: 35513103 DOI: 10.1016/j.ijbiomac.2022.04.205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2021] [Revised: 02/06/2022] [Accepted: 04/27/2022] [Indexed: 11/05/2022]
Abstract
Cataract is the most common pathogenic ophthalmic disease leading to blindness in children worldwide. Genetic disorder is the leading cause of congenital cataract, among which crystallin mutations have a high incidence. There are few reports on γA-crystallin, one critical member of crystallin superfamilies. In this study, we identified a novel pathogenic mutation (Ile82Met) in γA-crystallin from a three-generation Chinese family with cataract, and investigated the potential molecular mechanism in detail. To elucidate the pathogenic mechanism of I82M mutant, spectroscopic and solubility experiments were performed to determine the difference between the purified γA-crystallin wild type (WT) and I82M mutant under both physiological conditions and environmental stresses (UV irradiation, thermal denaturation or chemical denaturation). The I82M mutant did not affect the secondary/tertiary structure of monomeric γA-crystallin under physiological status, but decreased protein stability and increased aggregatory potency under the stressful treatment. Surprisingly, the chemical denaturation caused I82M to switch from the two-state unfolding of γA-crystallin to three-state unfolding involving an unfolding intermediate. This study expands the genetic variation map of cataract, and provides novel insights into the pathomechanism, in particular, filling in a gap in the understanding of γA-crystallin mutants causing cataract.
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Affiliation(s)
- Wanyue Xu
- The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou 310052, China; Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China; Institute of Translational Medicine, Zhejiang University School of Medicine, 268 Kaixuan Road, Hangzhou 310020, China
| | - Jingjie Xu
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China
| | - Caiping Shi
- The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou 310052, China
| | - Jing Wu
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China
| | - Huaxia Wang
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China; Institute of Translational Medicine, Zhejiang University School of Medicine, 268 Kaixuan Road, Hangzhou 310020, China
| | - Wei Wu
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China
| | - Xiangjun Chen
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China; Institute of Translational Medicine, Zhejiang University School of Medicine, 268 Kaixuan Road, Hangzhou 310020, China.
| | - Lidan Hu
- The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou 310052, China.
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13
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Schott RK, Bell RC, Loew ER, Thomas KN, Gower DJ, Streicher JW, Fujita MK. Transcriptomic evidence for visual adaptation during the aquatic to terrestrial metamorphosis in leopard frogs. BMC Biol 2022; 20:138. [PMID: 35761245 PMCID: PMC9238225 DOI: 10.1186/s12915-022-01341-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Accepted: 05/30/2022] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND Differences in morphology, ecology, and behavior through ontogeny can result in opposing selective pressures at different life stages. Most animals, however, transition through two or more distinct phenotypic phases, which is hypothesized to allow each life stage to adapt more freely to its ecological niche. How this applies to sensory systems, and in particular how sensory systems adapt across life stages at the molecular level, is not well understood. Here, we used whole-eye transcriptomes to investigate differences in gene expression between tadpole and juvenile southern leopard frogs (Lithobates sphenocephalus), which rely on vision in aquatic and terrestrial light environments, respectively. Because visual physiology changes with light levels, we also tested the effect of light and dark exposure. RESULTS We found 42% of genes were differentially expressed in the eyes of tadpoles versus juveniles and 5% for light/dark exposure. Analyses targeting a curated subset of visual genes revealed significant differential expression of genes that control aspects of visual function and development, including spectral sensitivity and lens composition. Finally, microspectrophotometry of photoreceptors confirmed shifts in spectral sensitivity predicted by the expression results, consistent with adaptation to distinct light environments. CONCLUSIONS Overall, we identified extensive expression-level differences in the eyes of tadpoles and juveniles related to observed morphological and physiological changes through metamorphosis and corresponding adaptive shifts to improve vision in the distinct aquatic and terrestrial light environments these frogs inhabit during their life cycle. More broadly, these results suggest that decoupling of gene expression can mediate the opposing selection pressures experienced by organisms with complex life cycles that inhabit different environmental conditions throughout ontogeny.
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Affiliation(s)
- Ryan K Schott
- Department of Biology, York University, Toronto, Ontario, Canada. .,Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington DC, USA.
| | - Rayna C Bell
- Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington DC, USA.,Department of Herpetology, California Academy of Sciences, San Francisco, CA, USA
| | - Ellis R Loew
- Department of Biomedical Sciences, Cornell University College of Veterinary Medicine, Ithaca, NY, USA
| | - Kate N Thomas
- Department of Life Sciences, The Natural History Museum, London, UK
| | - David J Gower
- Department of Life Sciences, The Natural History Museum, London, UK
| | | | - Matthew K Fujita
- Department of Biology, Amphibian and Reptile Diversity Research Center, The University of Texas at Arlington, Arlington, TX, USA
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14
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Strofaldi A, Khan AR, McManus JJ. Surface Exposed Free Cysteine Suppresses Crystallization of Human γD-Crystallin. J Mol Biol 2021; 433:167252. [PMID: 34537240 DOI: 10.1016/j.jmb.2021.167252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 09/06/2021] [Accepted: 09/09/2021] [Indexed: 11/28/2022]
Abstract
Human γD-crystallin (HGD) has remarkable stability against condensation in the human lens, sometimes over a whole lifetime. The native protein has a surface exposed free cysteine that forms dimers (Benedek, 1997; Ramkumar et al., 1864)1,2 without specific biological function and leads to further protein association and/or aggregation, which creates a paradox for understanding its stability. Previous work has demonstrated that chemical modification of the protein at the free cysteine (C110), increases the temperature at which liquid-liquid phase separation occurs (LLPS), lowers protein solubility and suggests an important role for this amino acid in maintaining its long-term resistance to condensation. Here we demonstrate that mutation of the cysteine does not alter the structure or solubility (liquidus) line for the protein, but dramatically increases the protein crystal nucleation rate following LLPS, suggesting that the free cysteine has a vital role in suppressing crystallization in the human lens.
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Affiliation(s)
- Alessandro Strofaldi
- Department of Chemistry, Maynooth University, Maynooth, Co. Kildare, Ireland; H. H Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, United Kingdom
| | - Amir R Khan
- Division of Newborn Medicine, Boston Children's Hospital, Boston, USA; School of Biochemistry, Trinity College Dublin, Ireland
| | - Jennifer J McManus
- H. H Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, United Kingdom.
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15
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Serebryany E, Thorn DC, Quintanar L. Redox chemistry of lens crystallins: A system of cysteines. Exp Eye Res 2021; 211:108707. [PMID: 34332989 PMCID: PMC8511183 DOI: 10.1016/j.exer.2021.108707] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Revised: 07/09/2021] [Accepted: 07/23/2021] [Indexed: 11/28/2022]
Abstract
The nuclear region of the lens is metabolically quiescent, but it is far from inert chemically. Without cellular renewal and with decades of environmental exposures, the lens proteome, lipidome, and metabolome change. The lens crystallins have evolved exquisite mechanisms for resisting, slowing, adapting to, and perhaps even harnessing the effects of these cumulative chemical modifications to minimize the amount of light-scattering aggregation in the lens over a lifetime. Redox chemistry is a major factor in these damages and mitigating adaptations, and as such, it is likely to be a key component of any successful therapeutic strategy for preserving or rescuing lens transparency, and perhaps flexibility, during aging. Protein redox chemistry is typically mediated by Cys residues. This review will therefore focus primarily on the Cys-rich γ-crystallins of the human lens, taking care to extend these findings to the β- and α-crystallins where pertinent.
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Affiliation(s)
- Eugene Serebryany
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA.
| | - David C Thorn
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
| | - Liliana Quintanar
- Department of Chemistry, Centro de Investigación y de Estudios Avanzados (Cinvestav), Mexico City, Mexico
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16
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Genetic Adaptations in Mudskipper and Tetrapod Give Insights into Their Convergent Water-to-Land Transition. Animals (Basel) 2021; 11:ani11020584. [PMID: 33672418 PMCID: PMC7926366 DOI: 10.3390/ani11020584] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 02/13/2021] [Accepted: 02/20/2021] [Indexed: 11/17/2022] Open
Abstract
Water-to-land transition has been independently evolved in multiple vertebrate lineages including the most recent common ancestor of tetrapod and multiple fish clades, and among them, mudskippers uniquely adapted to the mudflat. Even though physiological and morphological adaptation of mudskippers is thought to resemble that of the ancestral tetrapod, it is unclear if they share genome-wide evolutionary signatures. To detect potential signatures of positive selection in mudskipper and tetrapods, we analyzed 4118 singleton orthologues of terrestrial tetrapods, coelacanth, mudskipper, and fully aquatic fishes. Among positively selected genes identified in mudskipper and tetrapod lineages, genes involved in immune responses, mitochondrial oxidative phosphorylation, and kidney development were detected. On the other hand, tetrapod-specific and mudskipper-specific positively selected genes were functionally enriched for DNA repair processes, which could be associated with higher exposure to UV light. We also performed gene family analysis and discovered convergent contraction of eight gene families, including βγ-crystallin coding genes in both tetrapod and mudskipper lineages. Findings of this study suggest the similar genetic adaptation against environmental constraints between the ancient tetrapod and mudskippers for their land adaptation.
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17
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Velasco-Bolom JL, Domínguez L. Exploring the folding process of human βB2-crystallin using multiscale molecular dynamics and the Markov state model. Phys Chem Chem Phys 2021; 22:26753-26763. [PMID: 33205789 DOI: 10.1039/d0cp04136j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Adequate knowledge of protein conformations is crucial for understanding their function and their association properties with other proteins. The cataract disease is correlated with conformational changes in key proteins called crystallins. These changes are due to mutations or post-translational modifications that may lead to protein unfolding, and thus the formation of aggregate states. Human βB2-crystallin (HβB2C) is found in high proportion in the eye lens, and its mutations are related to some cataracts. HβB2C also associates into dimers, tetramers, and other higher-order supramolecular complexes. However, it is the only protein of the βγ-crystallin family that has been found in an extended conformation. Therefore, we hypothesize that the extended conformation is not energetically favourable and that HβB2C may adopt a closed (completely folded) conformation, similar to the other members of the βγ-crystallin family. To corroborate this hypothesis, we performed extensive molecular dynamics simulations of HβB2C in its monomeric and dimeric conformations, using all-atom and coarse-grained scales. We employed Markov state model (MSM) analysis to characterize the conformational and kinetically relevant states in the folding process of monomeric HβB2C. The MSM analysis clearly shows that HβB2C adopts a completely folded structure, and this conformation is the most kinetically and energetically favourable one. In contrast, the extended conformations are kinetically unstable and energetically unfavourable. Our MSM analysis also reveals a key metastable state, which is particularly interesting because it is from this state that the folded state is reached. The folded state is stabilized by the formation of two salt bridges between the residue-pairs E74-R187 and R97-E166 and the two hydrophobic residue-pairs V59-L164 and V72-V151. Furthermore, free energy surface (FES) analysis revealed that the HβB2C dimer with both monomers in a closed conformation (face-en-face dimer) is energetically more stable than the domain-swapped dimer (crystallographic structure). The results presented in this report shed light on the molecular details of the folding mechanism of HβB2C in an aqueous environment and may contribute to interpreting different experimental findings. Finally, a detailed knowledge of HβB2C folding may be key to the rational design of potential molecules to treat cataract disease.
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Affiliation(s)
- José-Luis Velasco-Bolom
- Facultad de Química, Departamento de Fisicoquímica, Universidad Nacional Autónoma de México, Mexico City, 04510, Mexico.
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18
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Abu-Hussien M, Viswanathan GK, Borisover L, Mimouni M, Engel H, Zayit-Soudry S, Gazit E, Segal D. Inhibition of amyloid fibrillation of γD-crystallin model peptide by the cochineal Carmine. Int J Biol Macromol 2020; 169:342-351. [PMID: 33347930 DOI: 10.1016/j.ijbiomac.2020.12.106] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 12/07/2020] [Accepted: 12/12/2020] [Indexed: 01/09/2023]
Abstract
γD-crystallin is among the most abundant γ-crystallins in the human eye lens which are essential for preserving its transparency. Aging, and environmental changes, cause crystallins to lose their native soluble structure and aggregate, resulting in the formation of cataract. Current treatment of cataract is surgical removal which is costly. Pharmaceutical therapeutics of cataract is an unmet need. We report a screen for small molecules capable of inhibiting aggregation of human γD-crystallin. Using a highly amyloidogenic hexapeptide model 41GCWMLY46 derived from the full-length protein, we screened a library of 68 anthraquinone molecules using ThT fluorescence assay. A leading hit, the cochineal Carmine, effectively reduced aggregation of the model GDC6 peptide in dose dependent manner. Similar effect was observed toward aggregation of the full-length γD-crystallin. Transmission electron microscopy, intrinsic Tryptophan fluorescence and ANS fluorescence assays corroborated these results. Insights obtained from molecular docking suggested that Carmine interaction with monomeric GDC6 involved hydrogen bonding with Ace group, Cys, Met residues and hydrophobic contact with Trp residue. Carmine was non-toxic toward retinal cells in culture. It also reduced ex vivo the turbidity of human extracted cataract material. Collectively, our results indicate that Carmine could be used for developing new therapeutics to treat cataract.
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Affiliation(s)
- Malak Abu-Hussien
- Department of Molecular Microbiology and Biotechnology, The Shmunis School of Biomedicine and Cancer Research, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Guru Krishnakumar Viswanathan
- Department of Molecular Microbiology and Biotechnology, The Shmunis School of Biomedicine and Cancer Research, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Lia Borisover
- Department of Molecular Microbiology and Biotechnology, The Shmunis School of Biomedicine and Cancer Research, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Michael Mimouni
- Department of Ophthalmology, Rambam Health Care Campus, Haifa, Israel; The Ruth and Bruce Rappaport Faculty of Medicine, Technion Israel Institute of Technology, Haifa, Israel
| | - Hamutal Engel
- Blavatnik Center for Drug Discovery, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Shiri Zayit-Soudry
- Department of Ophthalmology, Rambam Health Care Campus, Haifa, Israel; The Ruth and Bruce Rappaport Faculty of Medicine, Technion Israel Institute of Technology, Haifa, Israel
| | - Ehud Gazit
- Department of Molecular Microbiology and Biotechnology, The Shmunis School of Biomedicine and Cancer Research, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Daniel Segal
- Department of Molecular Microbiology and Biotechnology, The Shmunis School of Biomedicine and Cancer Research, Tel Aviv University, 69978 Tel Aviv, Israel; The Interdisciplinary Sagol School of Neurosciences, Tel Aviv University, 69978 Tel Aviv, Israel.
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19
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Guseman AJ, Whitley MJ, González JJ, Rathi N, Ambarian M, Gronenborn AM. Assessing the Structures and Interactions of γD-Crystallin Deamidation Variants. Structure 2020; 29:284-291.e3. [PMID: 33264606 DOI: 10.1016/j.str.2020.11.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Revised: 10/12/2020] [Accepted: 11/06/2020] [Indexed: 11/25/2022]
Abstract
Cataracts involve the deposition of the crystallin proteins in the vertebrate eye lens, causing opacification and blindness. They are associated with either genetic mutation or protein damage that accumulates over the lifetime of the organism. Deamidation of Asn residues in several different crystallins has been observed and is frequently invoked as a cause of cataract. Here, we investigated the properties of Asp variants, deamidation products of γD-crystallin, by solution NMR, X-ray crystallography, and other biophysical techniques. No substantive structural or stability changes were noted for all seven Asn to Asp γD-crystallins. Importantly, no changes in diffusion interaction behavior could be detected. Our combined experimental results demonstrate that introduction of single Asp residues on the surface of γD-crystallin by deamidation is unlikely to be the driver of cataract formation in the eye lens.
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Affiliation(s)
- Alex J Guseman
- Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 Fifth Avenue, Pittsburgh, PA 15261, USA
| | - Matthew J Whitley
- Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 Fifth Avenue, Pittsburgh, PA 15261, USA
| | - Jeremy J González
- Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 Fifth Avenue, Pittsburgh, PA 15261, USA
| | - Nityam Rathi
- Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 Fifth Avenue, Pittsburgh, PA 15261, USA
| | - Mikayla Ambarian
- Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 Fifth Avenue, Pittsburgh, PA 15261, USA
| | - Angela M Gronenborn
- Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 Fifth Avenue, Pittsburgh, PA 15261, USA.
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20
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Grosas AB, Rekas A, Mata JP, Thorn DC, Carver JA. The Aggregation of αB-Crystallin under Crowding Conditions Is Prevented by αA-Crystallin: Implications for α-Crystallin Stability and Lens Transparency. J Mol Biol 2020; 432:5593-5613. [PMID: 32827531 DOI: 10.1016/j.jmb.2020.08.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 08/13/2020] [Accepted: 08/13/2020] [Indexed: 02/08/2023]
Abstract
One of the most crowded biological environments is the eye lens which contains a high concentration of crystallin proteins. The molecular chaperones αB-crystallin (αBc) with its lens partner αA-crystallin (αAc) prevent deleterious crystallin aggregation and cataract formation. However, some forms of cataract are associated with structural alteration and dysfunction of αBc. While many studies have investigated the structure and function of αBc under dilute in vitro conditions, the effect of crowding on these aspects is not well understood despite its in vivo relevance. The structure and chaperone ability of αBc under conditions that mimic the crowded lens environment were investigated using the polysaccharide Ficoll 400 and bovine γ-crystallin as crowding agents and a variety of biophysical methods, principally contrast variation small-angle neutron scattering. Under crowding conditions, αBc unfolds, increases its size/oligomeric state, decreases its thermal stability and chaperone ability, and forms kinetically distinct amorphous and fibrillar aggregates. However, the presence of αAc stabilizes αBc against aggregation. These observations provide a rationale, at the molecular level, for the aggregation of αBc in the crowded lens, a process that exhibits structural and functional similarities to the aggregation of cataract-associated αBc mutants R120G and D109A under dilute conditions. Strategies that maintain or restore αBc stability, as αAc does, may provide therapeutic avenues for the treatment of cataract.
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Affiliation(s)
- Aidan B Grosas
- Research School of Chemistry, The Australian National University, Canberra, ACT, 2601, Australia
| | - Agata Rekas
- National Deuteration Facility, Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, NSW 2234, Australia
| | - Jitendra P Mata
- Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, NSW 2234, Australia
| | - David C Thorn
- Research School of Chemistry, The Australian National University, Canberra, ACT, 2601, Australia
| | - John A Carver
- Research School of Chemistry, The Australian National University, Canberra, ACT, 2601, Australia.
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21
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Wang K, Hoshino M, Uesugi K, Yagi N, Young RD, Frost BE, Regini JW, Quantock AJ, Pierscionek BK. Cell compaction is not required for the development of gradient refractive index profiles in the embryonic chick lens. Exp Eye Res 2020; 197:108112. [DOI: 10.1016/j.exer.2020.108112] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 06/01/2020] [Accepted: 06/03/2020] [Indexed: 01/30/2023]
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22
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Anderson DM, Nye-Wood MG, Rose KL, Donaldson PJ, Grey AC, Schey KL. MALDI imaging mass spectrometry of β- and γ-crystallins in the ocular lens. JOURNAL OF MASS SPECTROMETRY : JMS 2020; 55:e4473. [PMID: 31713937 PMCID: PMC8184062 DOI: 10.1002/jms.4473] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 10/21/2019] [Accepted: 10/30/2019] [Indexed: 06/10/2023]
Abstract
Lens crystallin proteins make up 90% of expressed proteins in the ocular lens and are primarily responsible for maintaining lens transparency and establishing the gradient of refractive index necessary for proper focusing of images onto the retina. Age-related modifications to lens crystallins have been linked to insolubilization and cataractogenesis in human lenses. Matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) has been shown to provide spatial maps of such age-related modifications. Previous work demonstrated that, under standard protein IMS conditions, α-crystallin signals dominated the mass spectrum and age-related modifications to α-crystallins could be mapped. In the current study, a new sample preparation method was optimized to allow imaging of β- and γ-crystallins in ocular lens tissue. Acquired images showed that γ-crystallins were localized predominately in the lens nucleus whereas β-crystallins were primarily localized to the lens cortex. Age-related modifications such as truncation, acetylation, and carbamylation were identified and spatially mapped. Protein identifications were determined by top-down proteomics analysis of lens proteins extracted from tissue sections and analyzed by LC-MS/MS with electron transfer dissociation. This new sample preparation method combined with the standard method allows the major lens crystallins to be mapped by MALDI IMS.
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Affiliation(s)
- David M. Anderson
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee
- Mass Spectrometry Research Center, Vanderbilt University, Nashville, Tennessee
| | | | - Kristie L. Rose
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee
- Mass Spectrometry Research Center, Vanderbilt University, Nashville, Tennessee
| | - Paul J. Donaldson
- New Zealand National Eye Centre, University of Auckland, Auckland, New Zealand
- School of Medical Sciences, University of Auckland, Auckland, New Zealand
| | - Angus C. Grey
- New Zealand National Eye Centre, University of Auckland, Auckland, New Zealand
- School of Medical Sciences, University of Auckland, Auckland, New Zealand
| | - Kevin L. Schey
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee
- Mass Spectrometry Research Center, Vanderbilt University, Nashville, Tennessee
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23
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Houston P, Macro N, Kang M, Chen L, Yang J, Wang L, Wu Z, Zhong D. Ultrafast Dynamics of Water-Protein Coupled Motions around the Surface of Eye Crystallin. J Am Chem Soc 2020; 142:3997-4007. [PMID: 31991083 PMCID: PMC7261499 DOI: 10.1021/jacs.9b13506] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Water dynamics on the protein surface mediate both protein structure and function. However, many questions remain about the role of the protein hydration layers in protein fluctuations and how the dynamics of these layers relate to specific protein properties. The fish eye lens protein γM7-crystallin (γM7) is found in vivo at extremely high concentrations nearing the packing limit, corresponding to only a few water layers between adjacent proteins. In this study, we conducted a site-specific probing of hydration water motions and side-chain dynamics at nine selected sites around the surface of γM7 using a tryptophan scan with femtosecond spectroscopy and NMR nuclear spin relaxation (NSR). We observed correlated fluctuations between hydration water and protein side chains on the time scales of a few picoseconds and hundreds of picoseconds, corresponding to local reorientations and network restructuring, respectively. These motions are heterogeneous over the protein surface and relate to the various steric and chemical properties of the local protein environment. Overall, we found that γM7 has relatively slower water dynamics within the hydration shell than a similar β-sheet protein, which may contribute to the high packing limit of this unique protein.
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Affiliation(s)
- Patrick Houston
- Department of Physics, Department of Chemistry and Biochemistry, and Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus Ohio, 43210, USA
| | - Nicolas Macro
- Department of Physics, Department of Chemistry and Biochemistry, and Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus Ohio, 43210, USA
| | - Minhee Kang
- Department of Physics, Department of Chemistry and Biochemistry, and Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus Ohio, 43210, USA
| | - Long Chen
- Department of Physics, Department of Chemistry and Biochemistry, and Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus Ohio, 43210, USA
| | - Jin Yang
- Department of Physics, Department of Chemistry and Biochemistry, and Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus Ohio, 43210, USA
| | - Lijuan Wang
- Department of Physics, Department of Chemistry and Biochemistry, and Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus Ohio, 43210, USA
| | - Zhengrong Wu
- Department of Physics, Department of Chemistry and Biochemistry, and Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus Ohio, 43210, USA
| | - Dongping Zhong
- Department of Physics, Department of Chemistry and Biochemistry, and Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus Ohio, 43210, USA
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24
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Guest PC. Two-Dimensional Gel Electrophoresis Combined with Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry Analysis of Eye Lens to Identify Biomarkers of Age-Related Cataract. Methods Mol Biol 2020; 2138:217-231. [PMID: 32219751 DOI: 10.1007/978-1-0716-0471-7_14] [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] [Indexed: 06/10/2023]
Abstract
This chapter describes the application of two-dimensional gel electrophoresis (2DGE) combined with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) in the analysis of rat eye lens proteins. The main purpose was to identify proteins that may serve as potential biomarkers in age-related cataract formation. This includes the family of proteins known as the crystallins. Structural proteins and enzymes involved antioxidant activities. In addition, we also analyzed lenses from other species to illustrate the potential of using this technique in clinical and preclinical biomarker studies.
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Affiliation(s)
- Paul C Guest
- Laboratory of Neuroproteomics, Department of Biochemistry and Tissue Biology, Institute of Biology, University of Campinas (UNICAMP), Campinas, SP, Brazil.
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25
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Tinoco A, Gonçalves J, Silva C, Cavaco-Paulo A, Ribeiro A. Crystallin Fusion Proteins Improve the Thermal Properties of Hair. Front Bioeng Biotechnol 2019; 7:298. [PMID: 31709253 PMCID: PMC6823552 DOI: 10.3389/fbioe.2019.00298] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 10/15/2019] [Indexed: 11/21/2022] Open
Abstract
Styling hair with straightening irons is a popular daily hair routine that significantly damage the hair keratin fiber due to the high temperature applied. In this study, we investigate the effect of two fusion proteins based on the human eye γD-crystallin conjugated with a keratin-based peptide (KP-Cryst Wt and KP-Cryst Mut) on hair exposed to thermal damage. The mutant form was designed to improve protein stability and promote interaction with the hair. Through the study, it was demonstrated the protection of Asian and Caucasian virgin hair's structure by the pretreatments with the KP-Cryst fusion proteins. After hair thermal exposure, a higher water content was quantified by TGA on the hair fibers pretreated with the fusion proteins (about 38% for the KP-Cryst Wt and 44% for the KP-Cryst Mut). Also, negligible alterations in hair fibers' stiffness were observed after iron application, demonstrating the proteins capacity to effectively prevent the conversion of keratin α-helix structure into β-sheets. The results proved the capacity of the fusion proteins to bind to hair and protect it against high temperatures', supporting the development of new formulations based on the KP-Cryst proteins.
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Affiliation(s)
- Ana Tinoco
- Centre of Biological Engineering, University of Minho, Braga, Portugal
| | - José Gonçalves
- Centre of Biological Engineering, University of Minho, Braga, Portugal
| | - Carla Silva
- Centre of Biological Engineering, University of Minho, Braga, Portugal
| | | | - Artur Ribeiro
- Centre of Biological Engineering, University of Minho, Braga, Portugal
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26
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Schey KL, Wang Z, Friedrich MG, Garland DL, Truscott RJW. Spatiotemporal changes in the human lens proteome: Critical insights into long-lived proteins. Prog Retin Eye Res 2019; 76:100802. [PMID: 31704338 DOI: 10.1016/j.preteyeres.2019.100802] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Revised: 10/24/2019] [Accepted: 10/30/2019] [Indexed: 12/15/2022]
Abstract
The ocular lens is a unique tissue that contains an age gradient of cells and proteins ranging from newly differentiated cells containing newly synthesized proteins to cells and proteins that are as old as the organism. Thus, the ocular lens is an excellent model for studying long-lived proteins (LLPs) and the effects of aging and post-translational modifications on protein structure and function. Given the architecture of the lens, with young fiber cells in the outer cortex and the oldest cells in the lens nucleus, spatially-resolved studies provide information on age-specific protein changes. In this review, experimental strategies and proteomic methods that have been used to examine age-related and cataract-specific changes to the human lens proteome are described. Measured spatio-temporal changes in the human lens proteome are summarized and reveal a highly consistent, time-dependent set of modifications observed in transparent human lenses. Such measurements have led to the discovery of cataract-specific modifications and the realization that many animal systems are unsuitable to study many of these modifications. Mechanisms of protein modifications such as deamidation, racemization, truncation, and protein-protein crosslinking are presented and the implications of such mechanisms for other long-lived proteins in other tissues are discussed in the context of age-related neurological diseases. A comprehensive understanding of LLP modifications will enhance our ability to develop new therapies for the delay, prevention or reversal of age-related diseases.
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Affiliation(s)
- Kevin L Schey
- Department of Biochemistry, Vanderbilt University, USA.
| | - Zhen Wang
- Department of Biochemistry, Vanderbilt University, USA
| | - Michael G Friedrich
- Illawarra Health and Medical Research Institute, University of Wollongong, Australia
| | | | - Roger J W Truscott
- Illawarra Health and Medical Research Institute, University of Wollongong, Australia
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27
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Bhat SP, Gangalum RK, Kim D, Mangul S, Kashyap RK, Zhou X, Elashoff D. Transcriptional profiling of single fiber cells in a transgenic paradigm of an inherited childhood cataract reveals absence of molecular heterogeneity. J Biol Chem 2019; 294:13530-13544. [PMID: 31243103 PMCID: PMC6746439 DOI: 10.1074/jbc.ra119.008853] [Citation(s) in RCA: 5] [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: 04/12/2019] [Revised: 06/21/2019] [Indexed: 11/06/2022] Open
Abstract
Our recent single-cell transcriptomic analysis has demonstrated that heterogeneous transcriptional activity attends molecular transition from the nascent to terminally differentiated fiber cells in the developing mouse lens. To understand the role of transcriptional heterogeneity in terminal differentiation and the functional phenotype (transparency) of this tissue, here we present a single-cell analysis of the developing lens, in a transgenic paradigm of an inherited pathology, known as the lamellar cataract. Cataracts hinder transmission of light into the eye. Lamellar cataract is the most prevalent bilateral childhood cataract. In this disease of early infancy, initially, the opacities remain confined to a few fiber cells, thus presenting an opportunity to investigate early molecular events that lead to cataractogenesis. We used a previously established paradigm that faithfully recapitulates this disease in transgenic mice. About 500 single fiber cells, manually isolated from a 2-day-old transgenic lens were interrogated individually for the expression of all known 17 crystallins and 78 other relevant genes using a Biomark HD (Fluidigm). We find that fiber cells from spatially and developmentally discrete regions of the transgenic (cataract) lens show remarkable absence of the heterogeneity of gene expression. Importantly, the molecular variability of cortical fiber cells, the hallmark of the WT lens, is absent in the transgenic cataract, suggesting absence of specific cell-type(s). Interestingly, we find a repetitive pattern of gene activity in progressive states of differentiation in the transgenic lens. This molecular dysfunction portends pathology much before the physical manifestations of the disease.
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Affiliation(s)
- Suraj P Bhat
- Stein Eye Institute, Geffen School of Medicine, University of California, Los Angeles, California 90095-7000
- Brain Research Institute, University of California, Los Angeles, California 90095-7000
- Molecular Biology Institute, University of California, Los Angeles, California 90095-7000
| | - Rajendra K Gangalum
- Stein Eye Institute, Geffen School of Medicine, University of California, Los Angeles, California 90095-7000
| | - Dongjae Kim
- Stein Eye Institute, Geffen School of Medicine, University of California, Los Angeles, California 90095-7000
| | - Serghei Mangul
- Department of Computer Science and Human Genetics, University of California, Los Angeles, California 90095-7000
| | - Raj K Kashyap
- Stein Eye Institute, Geffen School of Medicine, University of California, Los Angeles, California 90095-7000
| | - Xinkai Zhou
- Department of Medicine, University of California, Los Angeles, California 90095-7000
| | - David Elashoff
- Department of Medicine, University of California, Los Angeles, California 90095-7000
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28
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Kozłowski TM, Kröger RH. Constant lens fiber cell thickness in fish suggests crystallin transport to denucleated cells. Vision Res 2019; 162:29-34. [DOI: 10.1016/j.visres.2019.06.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2019] [Revised: 06/16/2019] [Accepted: 06/21/2019] [Indexed: 12/21/2022]
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29
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Mills-Henry IA, Thol SL, Kosinski-Collins MS, Serebryany E, King JA. Kinetic Stability of Long-Lived Human Lens γ-Crystallins and Their Isolated Double Greek Key Domains. Biophys J 2019; 117:269-280. [PMID: 31266635 DOI: 10.1016/j.bpj.2019.06.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2018] [Revised: 05/25/2019] [Accepted: 06/05/2019] [Indexed: 12/17/2022] Open
Abstract
The γ-crystallins of the eye lens nucleus are among the longest-lived proteins in the human body. Synthesized in utero, they must remain folded and soluble throughout adulthood to maintain lens transparency and avoid cataracts. γD- and γS-crystallin are two major monomeric crystallins of the human lens. γD-crystallin is concentrated in the oldest lens fiber cells, the lens nucleus, whereas γS-crystallin is concentrated in the younger cells of the lens cortex. The kinetic stability parameters of these two-domain proteins and their isolated domains were determined and compared. Kinetic unfolding experiments monitored by fluorescence spectroscopy in varying concentrations of guanidinium chloride were used to extrapolate unfolding rate constants and half-lives of the crystallins in the absence of the denaturant. Consistent with their long lifespans in the lens, extrapolated half-lives for the initial unfolding step were on the timescale of years. Both proteins' isolated N-terminal domains were less kinetically stable than their respective C-terminal domains at denaturant concentrations predicted to disrupt the domain interface, but at low denaturant concentrations, the relative kinetic stabilities were reversed. Cataract-associated aggregation has been shown to proceed from partially unfolded intermediates in these proteins; their extreme kinetic stability likely evolved to protect the lens from the initiation of aggregation reactions. Our findings indicate that the domain interface is the source of significant kinetic stability. The gene duplication and fusion event that produced the modern two-domain architecture of vertebrate lens crystallins may be the origin of their high kinetic as well as thermodynamic stability.
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Affiliation(s)
- Ishara A Mills-Henry
- Department of Chemistry and Food Science, Framingham State University, Framingham, Massachusetts
| | | | | | - Eugene Serebryany
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts.
| | - Jonathan A King
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts
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30
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Chaturvedi SK, Sagar V, Zhao H, Wistow G, Schuck P. Measuring Ultra-Weak Protein Self-Association by Non-ideal Sedimentation Velocity. J Am Chem Soc 2019; 141:2990-2996. [PMID: 30668114 PMCID: PMC6385077 DOI: 10.1021/jacs.8b11371] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
![]()
Ultra-weak self-association can govern
the macroscopic solution
behavior of concentrated macromolecular solutions ranging from food
products to pharmaceutical formulations and the cytosol. For example,
it can promote dynamic assembly of multi-protein signaling complexes,
lead to intracellular liquid–liquid phase transitions, and
seed crystallization or pathological aggregates. Unfortunately, weak
self-association is technically extremely difficult to study, as it
requires very high protein concentrations where short intermolecular
distances cause strongly correlated particle motion. Additionally,
protein samples near their solubility limit in vitro frequently show some degree of polydispersity. Here we exploit the
strong mass-dependent separation of assemblies in the centrifugal
field to study ultra-weak binding, using a sedimentation velocity
technique that allows us to determine particle size distributions
while accounting for colloidal hydrodynamic interactions and thermodynamic
non-ideality (Chaturvedi, S. K.; et al. Nat. Commun.2018, 9, 4415; DOI: 10.1038/s41467-018-06902-x). We show that this approach, applied to self-associating proteins,
can reveal a time-average association state for rapidly reversible
self-associations from which the free energy of binding can be derived.
The method is label-free and allows studying mid-sized proteins at
millimolar protein concentrations in a wide range of solution conditions.
We examine the performance of this method with hen egg lysozyme as
a model system, reproducing its well-known ionic-strength-dependent
weak self-association. The application to chicken γS-crystallin
reveals weak monomer–dimer self-association with KD = 24 mM, corresponding to a standard free energy change
of approximately −9 kJ/mol, which is a large contribution to
the delicate balance of forces ensuring eye lens transparency.
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Affiliation(s)
- Sumit K Chaturvedi
- Dynamics of Macromolecular Assembly Section, Laboratory of Cellular Imaging and Macromolecular Biophysics , National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health , Bethesda , Maryland 20892 , United States
| | - Vatsala Sagar
- Section on Molecular Structure and Functional Genomics, National Eye Institute , National Institutes of Health , Bethesda , Maryland 20892 , United States
| | - Huaying Zhao
- Dynamics of Macromolecular Assembly Section, Laboratory of Cellular Imaging and Macromolecular Biophysics , National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health , Bethesda , Maryland 20892 , United States
| | - Graeme Wistow
- Section on Molecular Structure and Functional Genomics, National Eye Institute , National Institutes of Health , Bethesda , Maryland 20892 , United States
| | - Peter Schuck
- Dynamics of Macromolecular Assembly Section, Laboratory of Cellular Imaging and Macromolecular Biophysics , National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health , Bethesda , Maryland 20892 , United States
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31
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Thorn DC, Grosas AB, Mabbitt PD, Ray NJ, Jackson CJ, Carver JA. The Structure and Stability of the Disulfide-Linked γS-Crystallin Dimer Provide Insight into Oxidation Products Associated with Lens Cataract Formation. J Mol Biol 2018; 431:483-497. [PMID: 30552875 DOI: 10.1016/j.jmb.2018.12.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 12/05/2018] [Indexed: 11/18/2022]
Abstract
The reducing environment in the eye lens diminishes with age, leading to significant oxidative stress. Oxidation of lens crystallin proteins is the major contributor to their destabilization and deleterious aggregation that scatters visible light, obscures vision, and ultimately leads to cataract. However, the molecular basis for oxidation-induced aggregation is unknown. Using X-ray crystallography and small-angle X-ray scattering, we describe the structure of a disulfide-linked dimer of human γS-crystallin that was obtained via oxidation of C24. The γS-crystallin dimer is stable at glutathione concentrations comparable to those in aged and cataractous lenses. Moreover, dimerization of γS-crystallin significantly increases the protein's propensity to form large insoluble aggregates owing to non-cooperative domain unfolding, as is observed in crystallin variants associated with early-onset cataract. These findings provide insight into how oxidative modification of crystallins contributes to cataract and imply that early-onset and age-related forms of the disease share comparable development pathways.
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Affiliation(s)
- David C Thorn
- Research School of Chemistry, The Australian National University, Acton, ACT 2601, Australia
| | - Aidan B Grosas
- Research School of Chemistry, The Australian National University, Acton, ACT 2601, Australia
| | - Peter D Mabbitt
- Research School of Chemistry, The Australian National University, Acton, ACT 2601, Australia
| | - Nicholas J Ray
- Research School of Chemistry, The Australian National University, Acton, ACT 2601, Australia
| | - Colin J Jackson
- Research School of Chemistry, The Australian National University, Acton, ACT 2601, Australia
| | - John A Carver
- Research School of Chemistry, The Australian National University, Acton, ACT 2601, Australia.
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32
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Gangalum RK, Kim D, Kashyap RK, Mangul S, Zhou X, Elashoff D, Bhat SP. Spatial Analysis of Single Fiber Cells of the Developing Ocular Lens Reveals Regulated Heterogeneity of Gene Expression. iScience 2018; 10:66-79. [PMID: 30508719 PMCID: PMC6277220 DOI: 10.1016/j.isci.2018.11.024] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 11/08/2018] [Accepted: 11/13/2018] [Indexed: 01/19/2023] Open
Abstract
The developing eye lens presents an exceptional paradigm for spatial transcriptomics. It is composed of highly organized long, slender transparent fiber cells, which differentiate from the edges of the anterior epithelium of the lens (equator), attended by high expression of crystallins, which generates transparency. Every fiber cell, therefore, is an optical unit whose refractive properties derive from its gene activity. Here, we probe this tangible relationship between the gene activity and the phenotype by studying the expression of all known 17 crystallins and 77 other non-crystallin genes in single fiber cells isolated from three states/regions of differentiation, allowing us to follow molecular progression at the single-cell level. The data demonstrate highly variable gene activity in cortical fibers, interposed between the nascent and the terminally differentiated fiber cell transcription. These data suggest that the so-called stochastic, highly heterogeneous gene activity is a regulated intermediate in the realization of a functional phenotype.
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Affiliation(s)
- Rajendra K Gangalum
- Stein Eye Institute, Geffen School of Medicine, University of California, Los Angeles, CA 90095-7000, USA
| | - Dongjae Kim
- Stein Eye Institute, Geffen School of Medicine, University of California, Los Angeles, CA 90095-7000, USA
| | - Raj K Kashyap
- Stein Eye Institute, Geffen School of Medicine, University of California, Los Angeles, CA 90095-7000, USA
| | - Serghei Mangul
- Department of Computer Science and Human Genetics, University of California, Los Angeles, CA 90095-7000, USA
| | - Xinkai Zhou
- Department of Medicine, University of California, Los Angeles, CA 90095-7000, USA
| | - David Elashoff
- Department of Medicine, University of California, Los Angeles, CA 90095-7000, USA
| | - Suraj P Bhat
- Stein Eye Institute, Geffen School of Medicine, University of California, Los Angeles, CA 90095-7000, USA; Brain Research Institute, University of California, Los Angeles, CA 90095-7000, USA; Molecular Biology Institute, University of California, Los Angeles, CA 90095-7000, USA.
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33
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Bierma JC, Roskamp KW, Ledray AP, Kiss AJ, Cheng CHC, Martin RW. Controlling Liquid-Liquid Phase Separation of Cold-Adapted Crystallin Proteins from the Antarctic Toothfish. J Mol Biol 2018; 430:5151-5168. [PMID: 30414964 DOI: 10.1016/j.jmb.2018.10.023] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2018] [Revised: 10/30/2018] [Accepted: 10/31/2018] [Indexed: 12/22/2022]
Abstract
Liquid-liquid phase separation (LLPS) of proteins is important to a variety of biological processes both functional and deleterious, including the formation of membraneless organelles, molecular condensations that sequester or release molecules in response to stimuli, and the early stages of disease-related protein aggregation. In the protein-rich, crowded environment of the eye lens, LLPS manifests as cold cataract. We characterize the LLPS behavior of six structural γ-crystallins from the eye lens of the Antarctic toothfish Dissostichus mawsoni, whose intact lenses resist cold cataract in subzero waters. Phase separation of these proteins is not strongly correlated with thermal stability, aggregation propensity, or cross-species chaperone protection from heat denaturation. Instead, LLPS is driven by protein-protein interactions involving charged residues. The critical temperature of the phase transition can be tuned over a wide temperature range by selective substitution of surface residues, suggesting general principles for controlling this phenomenon, even in compactly folded proteins.
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Affiliation(s)
- Jan C Bierma
- Department of Molecular Biology & Biochemistry, University of California, Irvine, CA 92697, USA
| | - Kyle W Roskamp
- Department of Chemistry, University of California, Irvine, CA 92697, USA
| | - Aaron P Ledray
- Department of Molecular Biology & Biochemistry, University of California, Irvine, CA 92697, USA
| | - Andor J Kiss
- Center for Bioinformatics and Functional Genomics, Miami University, Oxford, OH 45056,USA.
| | - C-H Christina Cheng
- Department of Animal Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801,USA
| | - Rachel W Martin
- Department of Molecular Biology & Biochemistry, University of California, Irvine, CA 92697, USA; Department of Chemistry, University of California, Irvine, CA 92697, USA.
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34
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Khago D, Bierma JC, Roskamp KW, Kozlyuk N, Martin RW. Protein refractive index increment is determined by conformation as well as composition. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:435101. [PMID: 30280702 PMCID: PMC6387658 DOI: 10.1088/1361-648x/aae000] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The refractive index gradient of the eye lens is controlled by the concentration and distribution of its component crystallin proteins, which are highly enriched in polarizable amino acids. The current understanding of the refractive index increment ([Formula: see text]) of proteins is described using an additive model wherein the refractivity and specific volume of each amino acid type contributes according to abundance in the primary sequence. Here we present experimental measurements of [Formula: see text] for crystallins from the human lens and those of aquatic animals under uniform solvent conditions. In all cases, the measured values are much higher than those predicted from primary sequence alone, suggesting that structural factors also contribute to protein refractive index.
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Affiliation(s)
- Domarin Khago
- Department of Chemistry, University of California, Irvine, CA 92697, United States of America
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35
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Measuring macromolecular size distributions and interactions at high concentrations by sedimentation velocity. Nat Commun 2018; 9:4415. [PMID: 30356043 PMCID: PMC6200768 DOI: 10.1038/s41467-018-06902-x] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 09/14/2018] [Indexed: 12/17/2022] Open
Abstract
In concentrated macromolecular solutions, weak physical interactions control the solution behavior including particle size distribution, aggregation, liquid-liquid phase separation, or crystallization. This is central to many fields ranging from colloid chemistry to cell biology and pharmaceutical protein engineering. Unfortunately, it is very difficult to determine macromolecular assembly states and polydispersity at high concentrations in solution, since all motion is coupled through long-range hydrodynamic, electrostatic, steric, and other interactions, and scattering techniques report on the solution structure when average interparticle distances are comparable to macromolecular dimensions. Here we present a sedimentation velocity technique that, for the first time, can resolve macromolecular size distributions at high concentrations, by simultaneously accounting for average mutual hydrodynamic and thermodynamic interactions. It offers high resolution and sensitivity of protein solutions up to 50 mg/ml, extending studies of macromolecular solution state closer to the concentration range of therapeutic formulations, serum, or intracellular conditions. Many aspects of concentrated macromolecular solutions, such as encountered in cytosol or in pharmaceutical formulations, are dependent on particle size distributions and weak intermolecular interactions. Here, the authors exploit hydrodynamic separation in the centrifugal field to measure both.
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36
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Laser interferometry of the hydrolytic changes in protein solutions: the refractive index and hydration shells. J Biol Phys 2018; 44:345-360. [PMID: 29752596 DOI: 10.1007/s10867-018-9494-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Accepted: 03/29/2018] [Indexed: 10/16/2022] Open
Abstract
Using an original laser interferometer of enhanced sensitivity, an increase in the refractive index of a protein solution was observed during the reaction of proteolysis catalyzed by pepsin. The increase in the refractive index of the protein solution at a concentration of 4 mg/ml was [Formula: see text] for bovine serum albumin and [Formula: see text] for lysozyme. The observed effect disproves the existing idea that the refractive index of protein solutions is determined only by their amino acid composition and concentration. It is shown that the refractive index also depends on the state of protein fragmentation. A mathematical model of proteolysis and a real-time method for estimating the state of protein hydration based on the measurement of refractive index during the reaction are proposed. A good agreement between the experimental and calculated time dependences of the refractive index shows that the growth of the surface of protein fragments and the change in the number of hydration cavities during proteolysis can be responsible for the observed effect.
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37
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Young LK, Jarrin M, Saunter CD, Quinlan RA, Girkin JM. Non-invasive in vivo quantification of the developing optical properties and graded index of the embryonic eye lens using SPIM. BIOMEDICAL OPTICS EXPRESS 2018; 9:2176-2188. [PMID: 29760979 PMCID: PMC5946780 DOI: 10.1364/boe.9.002176] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Revised: 03/22/2018] [Accepted: 03/23/2018] [Indexed: 06/08/2023]
Abstract
Graded refractive index lenses are inherent to advanced visual systems in animals. By understanding their formation and local optical properties, significant potential for improved ocular healthcare may be realized. We report a novel technique measuring the developing optical power of the eye lens, in a living animal, by exploiting the orthogonal imaging modality of a selective plane illumination microscope (SPIM). We have quantified the maturation of the lenticular refractive index at three different visible wavelengths using a combined imaging and ray tracing approach. We demonstrate that the method can be used with transgenic and vital dye labeling as well as with both fixed and living animals. Using a key eye lens morphogen and its inhibitor, we have measured their effects both on lens size and on refractive index. Our technique provides insights into the mechanisms involved in the development of this natural graded index micro-lens and its associated optical properties.
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Affiliation(s)
- Laura K Young
- Department of Physics, Durham University, South Road, Durham, DH1 3LE, UK
- Biophysical Sciences Institute, Durham University, South Road, Durham, DH1 3LE, UK
- Joint first authors
| | - Miguel Jarrin
- Biophysical Sciences Institute, Durham University, South Road, Durham, DH1 3LE, UK
- Department of Biosciences, Durham University, Upper Mountjoy, Stockton Road, Durham, DH1 3LE, UK
- Joint first authors
| | - Christopher D Saunter
- Department of Physics, Durham University, South Road, Durham, DH1 3LE, UK
- Biophysical Sciences Institute, Durham University, South Road, Durham, DH1 3LE, UK
| | - Roy A Quinlan
- Biophysical Sciences Institute, Durham University, South Road, Durham, DH1 3LE, UK
- Department of Biosciences, Durham University, Upper Mountjoy, Stockton Road, Durham, DH1 3LE, UK
| | - John M Girkin
- Department of Physics, Durham University, South Road, Durham, DH1 3LE, UK
- Biophysical Sciences Institute, Durham University, South Road, Durham, DH1 3LE, UK
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38
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Ray NJ, Hall D, Carver JA. A structural and functional study of Gln147 deamidation in αA-crystallin, a site of modification in human cataract. Exp Eye Res 2017; 161:163-173. [DOI: 10.1016/j.exer.2017.05.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Accepted: 05/16/2017] [Indexed: 10/19/2022]
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39
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Whitley MJ, Xi Z, Bartko JC, Jensen MR, Blackledge M, Gronenborn AM. A Combined NMR and SAXS Analysis of the Partially Folded Cataract-Associated V75D γD-Crystallin. Biophys J 2017; 112:1135-1146. [PMID: 28355541 DOI: 10.1016/j.bpj.2017.02.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Revised: 02/03/2017] [Accepted: 02/08/2017] [Indexed: 11/19/2022] Open
Abstract
A cataract is a pathological condition characterized by the clouding of the normally clear eye lens brought about by deposition of crystallin proteins in the lens fiber cells. These protein aggregates reduce visual acuity by scattering or blocking incoming light. Chemical damage to proteins of the crystallin family, accumulated over a lifetime, leads to age-related cataract, whereas inherited mutations are associated with congenital or early-onset cataract. The V75D mutant of γD-crystallin is associated with congenital cataract in mice and was previously shown to un/fold via a partially folded intermediate. Here, we structurally characterized the stable equilibrium urea unfolding intermediate of V75D at the ensemble level using solution NMR and small-angle x-ray scattering. Our data show that, in the intermediate, the C-terminal domain retains a folded conformation that is similar to the native wild-type protein, whereas the N-terminal domain is unfolded and comprises an ensemble of random conformers, without any detectable residual structural propensities.
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Affiliation(s)
- Matthew J Whitley
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Zhaoyong Xi
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Jonathan C Bartko
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | | | - Martin Blackledge
- Institut de Biologie Structurale, CEA, CNRS, Université Grenoble Alpes, Grenoble, France
| | - Angela M Gronenborn
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
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40
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Sagar V, Chaturvedi SK, Schuck P, Wistow G. Crystal Structure of Chicken γS-Crystallin Reveals Lattice Contacts with Implications for Function in the Lens and the Evolution of the βγ-Crystallins. Structure 2017. [PMID: 28648607 PMCID: PMC5518705 DOI: 10.1016/j.str.2017.05.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Previous attempts to crystallize mammalian γS-crystallin were unsuccessful. Native L16 chicken γS crystallized avidly while the Q16 mutant did not. The x-ray structure for chicken γS at 2.3Å resolution shows the canonical structure of the superfamily plus a well-ordered N-arm aligned with a β-sheet of a neighboring N-domain. L16 is also in a lattice contact, partially shielded from solvent. Unexpectedly, the major lattice contact matches a conserved interface (QR) in the multimeric β-crystallins. QR shows little conservation of residue contacts, except for one between symmetry-related tyrosines, but molecular dipoles for the proteins with QR show striking similarities while other γ-crystallins differ. In γS, QR has few hydrophobic contacts and features a thin layer of tightly bound water. The free energy of QR is slightly repulsive and AUC confirms no dimerization in solution. The lattice contacts suggest how γcrystallins allow close packing without aggregation in the crowded environment of the lens.
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Affiliation(s)
- Vatsala Sagar
- Section on Molecular Structure and Functional Genomics, National Eye Institute, National Institutes of Health, Building 6, Room 106, Bethesda, MD 20892, USA
| | - Sumit K Chaturvedi
- Dynamics of Macromolecular Assembly Section, LCIMB, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA
| | - Peter Schuck
- Dynamics of Macromolecular Assembly Section, LCIMB, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA
| | - Graeme Wistow
- Section on Molecular Structure and Functional Genomics, National Eye Institute, National Institutes of Health, Building 6, Room 106, Bethesda, MD 20892, USA.
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41
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Furuyama A, Matsushima C, Yokoi T, Ueda M, Tamiya E. Synthesis of Recombinant Mouse Crystallin Proteins and in Vitro Measurement of Their Refractivity. ACS Biomater Sci Eng 2017; 3:502-508. [PMID: 33429617 DOI: 10.1021/acsbiomaterials.6b00605] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The eye lens is an organ that focuses light onto the retina and is reported to have a high refractive index in vertebrates. An analysis of refractivity was conducted using recombinant mouse Crystallin proteins produced in Escherichia coli (E. coli) compared with bovine serum albumin (BSA) and other commercially available proteins. Not only did we measure the refractivity but for one of the crystallins, Cryba1, we also confirmed that it responds uniquely to its environmental conditions. The crystallin showed high refractivity, as expected, and we confirmed that the electrical charge of the Cryba1 molecule influences its refractivity.
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Affiliation(s)
- Akiho Furuyama
- Department of Applied Physics, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Chiyuki Matsushima
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
| | - Takahiro Yokoi
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
| | - Mitsuyoshi Ueda
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
| | - Eiichi Tamiya
- Department of Applied Physics, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
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42
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Sarimov RM, Matveyeva TA, Vasin AL, Binhi VN. Changes in the refractive index of a solution during proteolysis of bovine serum albumin with pepsin. Biophysics (Nagoya-shi) 2017. [DOI: 10.1134/s0006350917020221] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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43
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Messina-Baas O, Cuevas-Covarrubias SA. Inherited Congenital Cataract: A Guide to Suspect the Genetic Etiology in the Cataract Genesis. Mol Syndromol 2017; 8:58-78. [PMID: 28611546 DOI: 10.1159/000455752] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/05/2016] [Indexed: 01/23/2023] Open
Abstract
Cataracts are the principal cause of treatable blindness worldwide. Inherited congenital cataract (CC) shows all types of inheritance patterns in a syndromic and nonsyndromic form. There are more than 100 genes associated with cataract with a predominance of autosomal dominant inheritance. A cataract is defined as an opacity of the lens producing a variation of the refractive index of the lens. This variation derives from modifications in the lens structure resulting in light scattering, frequently a consequence of a significant concentration of high-molecular-weight protein aggregates. The aim of this review is to introduce a guide to identify the gene involved in inherited CC. Due to the manifold clinical and genetic heterogeneity, we discarded the cataract phenotype as a cardinal sign; a 4-group classification with the genes implicated in inherited CC is proposed. We consider that this classification will assist in identifying the probable gene involved in inherited CC.
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44
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Donaldson PJ, Grey AC, Maceo Heilman B, Lim JC, Vaghefi E. The physiological optics of the lens. Prog Retin Eye Res 2017; 56:e1-e24. [DOI: 10.1016/j.preteyeres.2016.09.002] [Citation(s) in RCA: 80] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Revised: 09/09/2016] [Accepted: 09/13/2016] [Indexed: 11/17/2022]
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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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Serebryany E, Takata T, Erickson E, Schafheimer N, Wang Y, King JA. Aggregation of Trp > Glu point mutants of human gamma-D crystallin provides a model for hereditary or UV-induced cataract. Protein Sci 2016; 25:1115-28. [PMID: 26991007 DOI: 10.1002/pro.2924] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Revised: 03/09/2016] [Accepted: 03/10/2016] [Indexed: 12/21/2022]
Abstract
Numerous mutations and covalent modifications of the highly abundant, long-lived crystallins of the eye lens cause their aggregation leading to progressive opacification of the lens, cataract. The nature and biochemical mechanisms of the aggregation process are poorly understood, as neither amyloid nor native-state polymers are commonly found in opaque lenses. The βγ-crystallin fold contains four highly conserved buried tryptophans, which can be oxidized to more hydrophilic products, such as kynurenine, upon UV-B irradiation. We mimicked this class of oxidative damage using Trp→Glu point mutants of human γD-crystallin. Such substitutions may represent a model of UV-induced photodamage-introduction of a charged group into the hydrophobic core generating "denaturation from within." The effects of Trp→Glu substitutions were highly position dependent. While each was destabilizing, only the two located in the bottom of the double Greek key fold-W42E and W130E-yielded robust aggregation of partially unfolded intermediates at 37°C and pH 7. The αB-crystallin chaperone suppressed aggregation of W130E, but not W42E, indicating distinct aggregation pathways from damage in the N-terminal vs C-terminal domain. The W130E aggregates had loosely fibrillar morphology, yet were nonamyloid, noncovalent, showed little surface hydrophobicity, and formed at least 20°C below the melting temperature of the native β-sheets. These features are most consistent with domain-swapped polymerization. Aggregation of partially destabilized crystallins under physiological conditions, as occurs in this class of point mutants, could provide a simple in vitro model system for drug discovery and optimization.
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Affiliation(s)
- Eugene Serebryany
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139
| | - Takumi Takata
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139
| | - Erika Erickson
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139
| | - Nathaniel Schafheimer
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139
| | - Yongting Wang
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139
| | - Jonathan A King
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139
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Bassnett S, Costello MJ. The cause and consequence of fiber cell compaction in the vertebrate lens. Exp Eye Res 2016; 156:50-57. [PMID: 26992780 DOI: 10.1016/j.exer.2016.03.009] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Revised: 03/02/2016] [Accepted: 03/11/2016] [Indexed: 01/02/2023]
Abstract
Fiber cells of the ocular lens are arranged in a series of concentric shells. New growth shells are added continuously to the lens surface and, as a consequence, the preexisting shells are buried. To focus light, the refractive index of the lens cytoplasm must exceed that of the surrounding aqueous and vitreous humors, and to that end, lens cells synthesize high concentrations of soluble proteins, the crystallins. To correct for spherical aberration, it is necessary that the crystallin concentration varies from shell-to-shell, such that cellular protein content is greatest in the center of the lens. The radial variation in protein content underlies the critical gradient index (GRIN) structure of the lens. Only the outermost shells of lens fibers contain the cellular machinery necessary for protein synthesis. It is likely, therefore, that the GRIN (which spans the synthetically inactive, organelle-free zone of the lens) does not result from increased levels of protein synthesis in the core of the lens but is instead generated through loss of volume by inner fiber cells. Because volume is lost primarily in the form of cell water, the residual proteins in the central lens fibers can be concentrated to levels of >500 mg/ml. In this short review, we describe the process of fiber cell compaction, its relationship to lens growth and GRIN formation, and offer some thoughts on the likely nature of the underlying mechanism.
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Affiliation(s)
- Steven Bassnett
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, USA.
| | - M Joseph Costello
- Department of Cell Biology and Physiology, University of North Carolina School of Medicine, USA
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Ray NJ, Hall D, Carver JA. Deamidation of N76 in human γS-crystallin promotes dimer formation. Biochim Biophys Acta Gen Subj 2015; 1860:315-24. [PMID: 26318015 DOI: 10.1016/j.bbagen.2015.08.015] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 06/28/2015] [Accepted: 08/24/2015] [Indexed: 10/23/2022]
Abstract
BACKGROUND Cataract formation is often attributed to the build-up of post-translational modifications in the crystallin proteins of the eye lens. One such modification, the deamidation of N76 in human γS-crystallin to D76, is highly correlated with age-related cataract (Hooi et al. Invest. Ophthalmol. Vis. Sci. 53 (2012) 3554-3561). In the current work, this modification has been extensively characterised in vitro. METHODS Biophysical characterisation was performed on wild type and N76D γS-crystallins using turbidity measurements to monitor aggregation, intrinsic fluorescence and circular dichroism spectroscopy to determine the folded state and NMR spectroscopy for identifying local changes in structure. Protein mass was determined using SEC-MALLS and analytical ultracentrifugation methods. RESULTS Relative to the wild type protein, deamidation at N76 in γS-crystallin causes an increase in the thermal stability and resistance to thermally induced aggregation alongside a decrease in stability to denaturants, a propensity to aggregate rapidly once destabilised and a tendency to form a dimer. We ascribe the apparent increase in thermal stability upon deamidation to the formation of dimer which prevents the unfolding of the inherently less stable monomer. CONCLUSIONS Deamidation causes a decrease in stability of γS-crystallin but this is offset by an increased tendency for dimer formation. GENERAL SIGNIFICANCE Deamidation at N76 in human γS-crystallin likely has a combinatorial effect with other post-translational crystallin modifications to induce age-related cataract. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.
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Affiliation(s)
- Nicholas J Ray
- Research School of Chemistry, The Australian National University, Acton, ACT 2601, Australia
| | - Damien Hall
- Research School of Chemistry, The Australian National University, Acton, ACT 2601, Australia
| | - John A Carver
- Research School of Chemistry, The Australian National University, Acton, ACT 2601, Australia.
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Biophysical chemistry of the ageing eye lens. Biophys Rev 2015; 7:353-368. [PMID: 28510099 DOI: 10.1007/s12551-015-0176-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Accepted: 06/23/2015] [Indexed: 12/24/2022] Open
Abstract
This review examines both recent and historical literature related to the biophysical chemistry of the proteins in the ageing eye, with a particular focus on cataract development. The lens is a vital component of the eye, acting as an optical focusing device to form clear images on the retina. The lens maintains the necessary high transparency and refractive index by expressing crystallin proteins in high concentration and eliminating all large cellular structures that may cause light scattering. This has the consequence of eliminating lens fibre cell metabolism and results in mature lens fibre cells having no mechanism for protein expression and a complete absence of protein recycling or turnover. As a result, the crystallins are some of the oldest proteins in the human body. Lack of protein repair or recycling means the lens tends to accumulate damage with age in the form of protein post-translational modifications. The crystallins can be subject to a wide range of age-related changes, including isomerisation, deamidation and racemisation. Many of these modification are highly correlated with cataract formation and represent a biochemical mechanism for age-related blindness.
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Pande A, Mokhor N, Pande J. Deamidation of Human γS-Crystallin Increases Attractive Protein Interactions: Implications for Cataract. Biochemistry 2015; 54:4890-9. [PMID: 26158710 DOI: 10.1021/acs.biochem.5b00185] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Deamidation of proteins is one of the most prevalent post-translational modifications found upon aging, and in age-onset diseases. Specific asparagine and glutamine residues are often selectively deamidated during this process. In the human lens, deamidation has been shown to occur in many crystallins, but it is not clear how these deamidated proteins lead to lens opacity or cataract. Here we have modeled in vitro the effect of deamidation of specific asparagine and glutamine residues in human recombinant γS-crystallin (HGS) on the solution properties of the protein. The residues selected for deamidation in vitro are those that are found to be deamidated in aged and cataractous lenses in vivo. Two derivatives were prepared, one with Asn76 and Asn143 deamidated (2N-HGS) and the other with two additional Gln residues (92 and 120) deamidated (2N2Q-HGS). Isoelectric focusing measurements showed the expected lowering of the pI from 6.9 in HGS to ∼6.5 in 2N-HGS and to ∼6.1 in 2N2Q-HGS. However, spectroscopic studies showed no significant change in the secondary and tertiary structures of the deamidated proteins relative to the wild type. The stability of 2N-HGS and 2N2Q-HGS, as measured by guanidinium hydrochloride unfolding, also remained comparable to that of HGS. The main difference was the altered protein-protein interaction among the three proteins. The net repulsive interactions that are characteristic of HGS are diminished in the deamidated derivatives as evidenced by static light scattering measurements of the second virial coefficient, B2 (B2 values for HGS, 2N-HGS, and 2N2Q-HGS of 8.90 × 10(-4), 7.10 × 10(-4), and 6.65 × 10(-4) mL mol g(-2), respectively). Further substantiation is provided by estimates of the excess binding energy of protein-protein interactions in the condensed phase, obtained from measurements of the PEG-induced liquid-liquid phase separation profiles for the three proteins. The data suggest that enhanced attractive protein-protein interactions, arising from the deamidation of HGS, promote protein aggregation, thereby leading to increased light scattering and opacity over time.
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Affiliation(s)
- Ajay Pande
- Department of Chemistry, Life Sciences 2070, University at Albany, State University of New York, Albany, New York 12222, United States
| | - Natalya Mokhor
- Department of Chemistry, Life Sciences 2070, University at Albany, State University of New York, Albany, New York 12222, United States
| | - Jayanti Pande
- Department of Chemistry, Life Sciences 2070, University at Albany, State University of New York, Albany, New York 12222, United States
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