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Donaldson PJ, Petrova RS, Nair N, Chen Y, Schey KL. Regulation of water flow in the ocular lens: new roles for aquaporins. J Physiol 2024; 602:3041-3056. [PMID: 37843390 PMCID: PMC11018719 DOI: 10.1113/jp284102] [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: 06/19/2023] [Accepted: 09/28/2023] [Indexed: 10/17/2023] Open
Abstract
The ocular lens is an important determinant of overall vision quality whose refractive and transparent properties change throughout life. The lens operates an internal microcirculation system that generates circulating fluxes of ions, water and nutrients that maintain the transparency and refractive properties of the lens. This flow of water generates a substantial hydrostatic pressure gradient which is regulated by a dual feedback system that uses the mechanosensitive channels TRPV1 and TRPV4 to sense decreases and increases, respectively, in the pressure gradient. This regulation of water flow (pressure) and hence overall lens water content, sets the two key parameters, lens geometry and the gradient of refractive index, which determine the refractive properties of the lens. Here we focus on the roles played by the aquaporin family of water channels in mediating lens water fluxes, with a specific focus on AQP5 as a regulated water channel in the lens. We show that in addition to regulating the activity of ion transporters, which generate local osmotic gradients that drive lens water flow, the TRPV1/4-mediated dual feedback system also modulates the membrane trafficking of AQP5 in the anterior influx pathway and equatorial efflux zone of the lens. Since both lens pressure and AQP5-mediated water permeability (P H 2 O ${P_{{{\mathrm{H}}_{\mathrm{2}}}{\mathrm{O}}}}$ ) can be altered by changes in the tension applied to the lens surface via modulating ciliary muscle contraction we propose extrinsic modulation of lens water flow as a potential mechanism to alter the refractive properties of the lens to ensure light remains focused on the retina throughout life.
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Affiliation(s)
- Paul J. Donaldson
- Department of Physiology, School of Medical Sciences, New Zealand National Eye Center, University of Auckland, Auckland, New Zealand
| | - Rosica S. Petrova
- Department of Physiology, School of Medical Sciences, New Zealand National Eye Center, University of Auckland, Auckland, New Zealand
| | - Nikhil Nair
- Department of Physiology, School of Medical Sciences, New Zealand National Eye Center, University of Auckland, Auckland, New Zealand
| | - Yadi Chen
- Department of Physiology, School of Medical Sciences, New Zealand National Eye Center, University of Auckland, Auckland, New Zealand
| | - Kevin L. Schey
- Department of Biochemistry, Vanderbilt University, Nashville, TN, 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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Vendra V, Thangapandian M. The importance of the fourth Greek key motif of human γD-crystallin in maintaining lens transparency-the tale told by the tail. Mol Vis 2024; 30:37-48. [PMID: 38586607 PMCID: PMC10994683] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Accepted: 02/10/2024] [Indexed: 04/09/2024] Open
Abstract
Purpose Congenital cataract affects 1-15 per 10,000 newborns worldwide, and 20,000-40,000 children are born every year with developmental bilateral cataracts. Mutations in the crystallin genes are known to cause congenital cataracts. Crystallins, proteins present in the eye lens, are made up of four Greek key motifs separated into two domains. Greek key motifs play an important role in compact folding to provide the necessary refractive index and transparency. The present study was designed to understand the importance of the fourth Greek key motif in maintaining lens transparency by choosing a naturally reported Y134X mutant human γD- crystallin in a Danish infant and its relationship to lens opacification and cataract. Methods Human γD-crystallin complementary DNA (cDNA) was cloned into the pET-21a vector, and the Y134X mutant clone was generated by site-directed mutagenesis. Wild-type and mutant proteins were overexpressed in the BL21 DE3 pLysS cells of E. coli. Wild-type protein was purified from the soluble fraction using the ion exchange and gel filtration chromatography methods. Mutant protein was predominantly found in insoluble fraction and purified from inclusion bodies. The structure, stability, aggregational, and amyloid fibril formation properties of the mutant were compared to those of the wild type using the fluorescence and circular dichroism spectroscopy methods. Results Loss of the fourth Greek key motif in human γD-crystallin affects the backbone conformation, alters the tryptophan micro-environment, and exposes a nonpolar hydrophobic core to the surface. Mutant is less stable and opens its Greek key motifs earlier with a concentration midpoint (CM) of unfolding curve of 1.5 M compared to the wild type human γD-crystallin (CM: 2.5 M). Mutant is capable of forming self-aggregates immediately in response to heating at 48.6 °C. Conclusions Loss of 39 amino acids in the fourth Greek key motif of human γD-crystallin affects the secondary and tertiary structures and exposes the hydrophobic residues to the solvent. These changes make the molecule less stable, resulting in the formation of light-scattering particles, which explains the importance of the fourth Greek key in the underlying mechanism of opacification and cataract.
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Affiliation(s)
- VenkataPullaRao Vendra
- Ophthalmic Molecular Genetics Section, Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, MD
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4
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Duot M, Viel R, Viet J, Le Goff-Gaillard C, Paillard L, Lachke SA, Gautier-Courteille C, Reboutier D. Eye Lens Organoids Made Simple: Characterization of a New Three-Dimensional Organoid Model for Lens Development and Pathology. Cells 2023; 12:2478. [PMID: 37887322 PMCID: PMC10605248 DOI: 10.3390/cells12202478] [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: 07/31/2023] [Revised: 10/09/2023] [Accepted: 10/13/2023] [Indexed: 10/28/2023] Open
Abstract
Cataract, the opacification of the lens, is the leading cause of blindness worldwide. Although effective, cataract surgery is costly and can lead to complications. Toward identifying alternate treatments, it is imperative to develop organoid models relevant for lens studies and drug screening. Here, we demonstrate that by culturing mouse lens epithelial cells under defined three-dimensional (3D) culture conditions, it is possible to generate organoids that display optical properties and recapitulate many aspects of lens organization and biology. These organoids can be rapidly produced in large amounts. High-throughput RNA sequencing (RNA-seq) on specific organoid regions isolated via laser capture microdissection (LCM) and immunofluorescence assays demonstrate that these lens organoids display a spatiotemporal expression of key lens genes, e.g., Jag1, Pax6, Prox1, Hsf4 and Cryab. Further, these lens organoids are amenable to the induction of opacities. Finally, the knockdown of a cataract-linked RNA-binding protein encoding gene, Celf1, induces opacities in these organoids, indicating their use in rapidly screening for genes that are functionally relevant to lens biology and cataract. In sum, this lens organoid model represents a compelling new tool to advance the understanding of lens biology and pathology and can find future use in the rapid screening of compounds aimed at preventing and/or treating cataracts.
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Affiliation(s)
- Matthieu Duot
- CNRS, UMR 6290, Institut de Génétique et Développement de Rennes (IGDR), Université de Rennes, 35000 Rennes, France
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
| | - Roselyne Viel
- CNRS, Inserm UMS Biosit, H2P2 Core Facility, Université de Rennes, 35000 Rennes, France
| | - Justine Viet
- CNRS, UMR 6290, Institut de Génétique et Développement de Rennes (IGDR), Université de Rennes, 35000 Rennes, France
| | - Catherine Le Goff-Gaillard
- CNRS, UMR 6290, Institut de Génétique et Développement de Rennes (IGDR), Université de Rennes, 35000 Rennes, France
| | - Luc Paillard
- CNRS, UMR 6290, Institut de Génétique et Développement de Rennes (IGDR), Université de Rennes, 35000 Rennes, France
| | - Salil A. Lachke
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
- Center for Bioinformatics and Computational Biology, University of Delaware, Newark, DE 19716, USA
| | - Carole Gautier-Courteille
- CNRS, UMR 6290, Institut de Génétique et Développement de Rennes (IGDR), Université de Rennes, 35000 Rennes, France
| | - David Reboutier
- CNRS, UMR 6290, Institut de Génétique et Développement de Rennes (IGDR), Université de Rennes, 35000 Rennes, France
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5
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Dias AMGC, Moreira IP, Lychko I, Lopes Soares C, Nurrito A, Moura Barbosa AJ, Lutz-Bueno V, Mezzenga R, Carvalho AL, Pina AS, Roque ACA. Hierarchical self-assembly of a reflectin-derived peptide. Front Chem 2023; 11:1267563. [PMID: 37810582 PMCID: PMC10552760 DOI: 10.3389/fchem.2023.1267563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Accepted: 09/05/2023] [Indexed: 10/10/2023] Open
Abstract
Reflectins are a family of intrinsically disordered proteins involved in cephalopod camouflage, making them an interesting source for bioinspired optical materials. Understanding reflectin assembly into higher-order structures by standard biophysical methods enables the rational design of new materials, but it is difficult due to their low solubility. To address this challenge, we aim to understand the molecular self-assembly mechanism of reflectin's basic unit-the protopeptide sequence YMDMSGYQ-as a means to understand reflectin's assembly phenomena. Protopeptide self-assembly was triggered by different environmental cues, yielding supramolecular hydrogels, and characterized by experimental and theoretical methods. Protopeptide films were also prepared to assess optical properties. Our results support the hypothesis for the protopeptide aggregation model at an atomistic level, led by hydrophilic and hydrophobic interactions mediated by tyrosine residues. Protopeptide-derived films were optically active, presenting diffuse reflectance in the visible region of the light spectrum. Hence, these results contribute to a better understanding of the protopeptide structural assembly, crucial for the design of peptide- and reflectin-based functional materials.
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Affiliation(s)
- Ana Margarida Gonçalves Carvalho Dias
- Associate Laboratory i4HB—Institute for Health and Bioeconomy, School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
- UCIBIO—Applied Molecular Biosciences Unit, Department of Chemistry, School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
| | - Inês Pimentel Moreira
- Associate Laboratory i4HB—Institute for Health and Bioeconomy, School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
- UCIBIO—Applied Molecular Biosciences Unit, Department of Chemistry, School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
| | - Iana Lychko
- Associate Laboratory i4HB—Institute for Health and Bioeconomy, School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
- UCIBIO—Applied Molecular Biosciences Unit, Department of Chemistry, School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
| | - Cátia Lopes Soares
- Associate Laboratory i4HB—Institute for Health and Bioeconomy, School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
- UCIBIO—Applied Molecular Biosciences Unit, Department of Chemistry, School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
| | - Arianna Nurrito
- Associate Laboratory i4HB—Institute for Health and Bioeconomy, School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
- UCIBIO—Applied Molecular Biosciences Unit, Department of Chemistry, School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
| | - Arménio Jorge Moura Barbosa
- Associate Laboratory i4HB—Institute for Health and Bioeconomy, School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
- UCIBIO—Applied Molecular Biosciences Unit, Department of Chemistry, School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
| | - Viviane Lutz-Bueno
- Department of Health Sciences and Technology, ETH Zürich, Zürich, Switzerland
- Paul Scherrer Institute, Villigen, Switzerland
| | - Raffaele Mezzenga
- Department of Health Sciences and Technology, ETH Zürich, Zürich, Switzerland
| | - Ana Luísa Carvalho
- Associate Laboratory i4HB—Institute for Health and Bioeconomy, School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
- UCIBIO—Applied Molecular Biosciences Unit, Department of Chemistry, School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
| | - Ana Sofia Pina
- Associate Laboratory i4HB—Institute for Health and Bioeconomy, School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
- UCIBIO—Applied Molecular Biosciences Unit, Department of Chemistry, School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
| | - Ana Cecília Afonso Roque
- Associate Laboratory i4HB—Institute for Health and Bioeconomy, School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
- UCIBIO—Applied Molecular Biosciences Unit, Department of Chemistry, School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
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6
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Rolland AD, Takata T, Donor MT, Lampi KJ, Prell JS. Eye lens β-crystallins are predicted by native ion mobility-mass spectrometry and computations to form compact higher-ordered heterooligomers. Structure 2023; 31:1052-1064.e3. [PMID: 37453416 PMCID: PMC10528727 DOI: 10.1016/j.str.2023.06.013] [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: 10/24/2022] [Revised: 05/04/2023] [Accepted: 06/20/2023] [Indexed: 07/18/2023]
Abstract
Eye lens α- and β-/γ-crystallin proteins are not replaced after fiber cell denucleation and maintain lens transparency and refractive properties. The exceptionally high (∼400-500 mg/mL) concentration of crystallins in mature lens tissue and multiple other factors impede precise characterization of β-crystallin interactions, oligomer composition, size, and topology. Native ion mobility-mass spectrometry is used here to probe β-crystallin association and provide insight into homo- and heterooligomerization kinetics for these proteins. These experiments include separation and characterization of higher-order β-crystallin oligomers and illustrate the unique advantages of native IM-MS. Recombinantly expressed βB1, βB2, and βA3 isoforms are found to have different homodimerization propensities, and only βA3 forms larger homooligomers. Heterodimerization of βB2 with βA3 occurs ∼3 times as fast as that of βB1 with βA3, and βB1 and βB2 heterodimerize less readily. Ion mobility experiments, molecular dynamics simulations, and PISA analysis together reveal that observed oligomers are consistent with predominantly compact, ring-like topologies.
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Affiliation(s)
- Amber D Rolland
- Department of Chemistry and Biochemistry, 1253 University of Oregon, Eugene, OR 97403-1253, USA
| | - Takumi Takata
- Kyoto University, Research Reactor Institute 2, Asashiro-Nishi, Kumatori-cho, Sennan-gun, Osaka 590-0494, Japan
| | - Micah T Donor
- Department of Biological & Molecular Sciences, George Fox University, 414 N Meridian St, Newberg, OR 97132, USA
| | - Kirsten J Lampi
- Integrative Biosciences, School of Dentistry, 3181 SW Sam Jackson Park Road, Oregon Health & Science University, Portland, OR 97239-3098, USA.
| | - James S Prell
- Department of Chemistry and Biochemistry, 1253 University of Oregon, Eugene, OR 97403-1253, USA; Materials Science Institute, 1252 University of Oregon, Eugene, OR 97403-1252, USA.
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7
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Rodriguez J, Tan Q, Šikić H, Taber LA, Bassnett S. The effect of fibre cell remodelling on the power and optical quality of the lens. J R Soc Interface 2023; 20:20230316. [PMID: 37727073 PMCID: PMC10509584 DOI: 10.1098/rsif.2023.0316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Accepted: 08/22/2023] [Indexed: 09/21/2023] Open
Abstract
Vertebrate eye lenses are uniquely adapted to form a refractive index gradient (GRIN) for improved acuity, and to grow slowly in size despite constant cell proliferation. The mechanisms behind these adaptations remain poorly understood. We hypothesize that cell compaction contributes to both. To test this notion, we examined the relationship between lens size and shape, refractive characteristics and the cross-sectional areas of constituent fibre cells in mice of different ages. We developed a block-face imaging method to visualize cellular cross sections and found that the cross-sectional areas of fibre cells rose and then decreased over time, with the most significant reduction occurring in denucleating cells in the adult lens cortex, followed by cells in the embryonic nucleus. These findings help reconcile differences between the predictions of lens growth models and empirical data. Biomechanical simulations suggested that compressive forces generated from continuous deposition of fibre cells could contribute to cellular compaction. However, optical measurements revealed that the GRIN did not mirror the pattern of cellular compaction, implying that compaction alone cannot account for GRIN formation and that additional mechanisms are likely to be involved.
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Affiliation(s)
- J. Rodriguez
- Department of Basic Sciences, University of Health Sciences and Pharmacy in St. Louis, 1 Pharmacy Place, St. Louis, MO 63110, USA
| | - Q. Tan
- Department of Ophthalmology & Visual Sciences, Washington University School of Medicine, 660 South Euclid Ave, Campus Box 8096, St. Louis, MO 63110, USA
| | - H. Šikić
- Department of Mathematics, Faculty of Science, University of Zagreb, Zagreb, Croatia
| | - L. A. Taber
- Department of Biomedical Engineering, Washington University, St. Louis, MO 63130, USA
| | - S. Bassnett
- Department of Ophthalmology & Visual Sciences, Washington University School of Medicine, 660 South Euclid Ave, Campus Box 8096, St. Louis, MO 63110, USA
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8
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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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9
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Halling DB, Philpo AE, Aldrich RW. Calcium dependence of both lobes of calmodulin is involved in binding to a cytoplasmic domain of SK channels. eLife 2022; 11:e81303. [PMID: 36583726 PMCID: PMC9803350 DOI: 10.7554/elife.81303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Accepted: 12/15/2022] [Indexed: 12/31/2022] Open
Abstract
KCa2.1-3 Ca2+-activated K+-channels (SK) require calmodulin to gate in response to cellular Ca2+. A model for SK gating proposes that the N-terminal domain (N-lobe) of calmodulin is required for activation, but an immobile C-terminal domain (C-lobe) has constitutive, Ca2+-independent binding. Although structures support a domain-driven hypothesis of SK gate activation by calmodulin, only a partial understanding is possible without measuring both channel activity and protein binding. We measured SK2 (KCa2.2) activity using inside-out patch recordings. Currents from calmodulin-disrupted SK2 channels can be restored with exogenously applied calmodulin. We find that SK2 activity only approaches full activation with full-length calmodulin with both an N- and a C-lobe. We measured calmodulin binding to a C-terminal SK peptide (SKp) using both composition-gradient multi-angle light-scattering and tryptophan emission spectra. Isolated lobes bind to SKp with high affinity, but isolated lobes do not rescue SK2 activity. Consistent with earlier models, N-lobe binding to SKp is stronger in Ca2+, and C-lobe-binding affinity is strong independent of Ca2+. However, a native tryptophan in SKp is sensitive to Ca2+ binding to both the N- and C-lobes of calmodulin at Ca2+ concentrations that activate SK2, demonstrating that the C-lobe interaction with SKp changes with Ca2+. Our peptide-binding data and electrophysiology show that SK gating models need deeper scrutiny. We suggest that the Ca2+-dependent associations of both lobes of calmodulin to SKp are crucial events during gating. Additional investigations are necessary to complete a mechanistic gating model consistent with binding, physiology, and structure.
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Affiliation(s)
- David B Halling
- Department of Neuroscience, The University of Texas at AustinAustinUnited States
| | - Ashley E Philpo
- Department of Neuroscience, The University of Texas at AustinAustinUnited States
| | - Richard W Aldrich
- Department of Neuroscience, The University of Texas at AustinAustinUnited States
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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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Lavania A, Carpenter WB, Oltrogge LM, Perez D, Turnšek JB, Savage DF, Moerner WE. Exploring Masses and Internal Mass Distributions of Single Carboxysomes in Free Solution Using Fluorescence and Interferometric Scattering in an Anti-Brownian Trap. J Phys Chem B 2022; 126:8747-8759. [PMID: 36282790 PMCID: PMC9639131 DOI: 10.1021/acs.jpcb.2c05939] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Carboxysomes are self-assembled bacterial microcompartments that facilitate carbon assimilation by colocalizing the enzymes of CO2 fixation within a protein shell. These microcompartments can be highly heterogeneous in their composition and filling, so measuring the mass and loading of an individual carboxysome would allow for better characterization of its assembly and function. To enable detailed and extended characterizations of single nanoparticles in solution, we recently demonstrated an improved interferometric scattering anti-Brownian electrokinetic (ISABEL) trap, which tracks the position of a single nanoparticle via its scattering of a near-infrared beam and applies feedback to counteract its Brownian motion. Importantly, the scattering signal can be related to the mass of nanoscale proteinaceous objects, whose refractive indices are well-characterized. We calibrate single-particle scattering cross-section measurements in the ISABEL trap and determine individual carboxysome masses in the 50-400 MDa range by analyzing their scattering cross sections with a core-shell model. We further investigate carboxysome loading by combining mass measurements with simultaneous fluorescence reporting from labeled internal components. This method may be extended to other biological objects, such as viruses or extracellular vesicles, and can be combined with orthogonal fluorescence reporters to achieve precise physical and chemical characterization of individual nanoscale biological objects.
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Affiliation(s)
- Abhijit
A. Lavania
- Department
of Chemistry, Stanford University, Stanford, California94305, United States,Department
of Applied Physics, Stanford University, Stanford, California94305, United States
| | - William B. Carpenter
- Department
of Chemistry, Stanford University, Stanford, California94305, United States
| | - Luke M. Oltrogge
- Department
of Molecular and Cell Biology, University
of California Berkeley, Berkeley, California94720, United States
| | - Davis Perez
- Department
of Chemistry, Stanford University, Stanford, California94305, United States
| | - Julia B. Turnšek
- Department
of Molecular and Cell Biology, University
of California Berkeley, Berkeley, California94720, United States
| | - David F. Savage
- Department
of Molecular and Cell Biology, University
of California Berkeley, Berkeley, California94720, United States
| | - W. E. Moerner
- Department
of Chemistry, Stanford University, Stanford, California94305, United States,Department
of Applied Physics, Stanford University, Stanford, California94305, United States,
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12
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Quinlan RA, Clark JI. Insights into the biochemical and biophysical mechanisms mediating the longevity of the transparent optics of the eye lens. J Biol Chem 2022; 298:102537. [PMID: 36174677 PMCID: PMC9638808 DOI: 10.1016/j.jbc.2022.102537] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 09/20/2022] [Accepted: 09/22/2022] [Indexed: 11/18/2022] Open
Abstract
In the human eye, a transparent cornea and lens combine to form the "refracton" to focus images on the retina. This requires the refracton to have a high refractive index "n," mediated largely by extracellular collagen fibrils in the corneal stroma and the highly concentrated crystallin proteins in the cytoplasm of the lens fiber cells. Transparency is a result of short-range order in the spatial arrangement of corneal collagen fibrils and lens crystallins, generated in part by post-translational modifications (PTMs). However, while corneal collagen is remodeled continuously and replaced, lens crystallins are very long-lived and are not replaced and so accumulate PTMs over a lifetime. Eventually, a tipping point is reached when protein aggregation results in increased light scatter, inevitably leading to the iconic protein condensation-based disease, age-related cataract (ARC). Cataracts account for 50% of vision impairment worldwide, affecting far more people than other well-known protein aggregation-based diseases. However, because accumulation of crystallin PTMs begins before birth and long before ARC presents, we postulate that the lens protein PTMs contribute to a "cataractogenic load" that not only increases with age but also has protective effects on optical function by stabilizing lens crystallins until a tipping point is reached. In this review, we highlight decades of experimental findings that support the potential for PTMs to be protective during normal development. We hypothesize that ARC is preventable by protecting the biochemical and biophysical properties of lens proteins needed to maintain transparency, refraction, and optical function.
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Affiliation(s)
- Roy A Quinlan
- Department of Biosciences, Durham University, South Road Science Site, Durham, United Kingdom; Department of Biological Structure, University of Washington, Seattle, Washington, USA.
| | - John I Clark
- Department of Biological Structure, University of Washington, Seattle, Washington, USA.
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13
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Mollusc Crystallins: Physical and Chemical Properties and Phylogenetic Analysis. DIVERSITY 2022. [DOI: 10.3390/d14100827] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The purpose of the present study was to perform bioinformatic analysis of crystallin diversity in aquatic molluscs based on the sequences in the NCBI Protein database. The objectives were as follows: (1) analysis of some physical and chemical properties of mollusc crystallins, (2) comparison of mollusc crystallins with zebrafish and cubomedusa Tripedalia cystophora crystallins, and (3) determination of the most probable candidates for the role of gastropod eye crystallins. The calculated average GRAVY values revealed that the majority of the seven crystallin groups, except for μ- and ζ-crystallins, were hydrophilic proteins. The predominant predicted secondary structures of the crystallins in most cases were α-helices and coils. The highest values of refractive index increment (dn/dc) were typical for crystallins of aquatic organisms with known lens protein composition (zebrafish, cubomedusa, and octopuses) and for S-crystallin of Pomacea canaliculata. The evolutionary relationships between the studied crystallins, obtained from multiple sequence alignments using Clustal Omega and MUSCLE, and the normalized conservation index, calculated by Mirny, showed that the most conservative proteins were Ω-crystallins but the most diverse were S-crystallins. The phylogenetic analysis of crystallin was generally consistent with modern mollusc taxonomy. Thus, α- and S-, and, possibly, J1A-crystallins, can be assumed to be the most likely candidates for the role of gastropod lens crystallins.
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14
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At the Intersection of Natural Structural Coloration and Bioengineering. Biomimetics (Basel) 2022; 7:biomimetics7020066. [PMID: 35645193 PMCID: PMC9149877 DOI: 10.3390/biomimetics7020066] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Revised: 05/11/2022] [Accepted: 05/12/2022] [Indexed: 02/04/2023] Open
Abstract
Most of us get inspired by and interact with the world around us based on visual cues such as the colors and patterns that we see. In nature, coloration takes three primary forms: pigmentary coloration, structural coloration, and bioluminescence. Typically, pigmentary and structural coloration are used by animals and plants for their survival; however, few organisms are able to capture the nearly instantaneous and visually astounding display that cephalopods (e.g., octopi, squid, and cuttlefish) exhibit. Notably, the structural coloration of these cephalopods critically relies on a unique family of proteins known as reflectins. As a result, there is growing interest in characterizing the structure and function of such optically-active proteins (e.g., reflectins) and to leverage these materials across a broad range of disciplines, including bioengineering. In this review, I begin by briefly introducing pigmentary and structural coloration in animals and plants as well as highlighting the extraordinary appearance-changing capabilities of cephalopods. Next, I outline recent advances in the characterization and utilization of reflectins for photonic technologies and and discuss general strategies and limitations for the structural and optical characterization of proteins. Finally, I explore future directions of study for optically-active proteins and their potential applications. Altogether, this review aims to bring together an interdisciplinary group of researchers who can resolve the fundamental questions regarding the structure, function, and self-assembly of optically-active protein-based materials.
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15
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Zeng H, Zhang Y, Ma Y, Li S. Electromagnetic modeling and simulation of the biophoton propagation in myelinated axon waveguide. APPLIED OPTICS 2022; 61:4013-4021. [PMID: 36256074 DOI: 10.1364/ao.446845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Accepted: 04/21/2022] [Indexed: 06/16/2023]
Abstract
Biophotons in the nervous system are a potential carrier of neural signals. Previous experiments and studies indicated that biophotons are closely related to the neuronal activity and can propagate along myelinated axons. We establish a multilayer electromagnetic simulation model and demonstrate that the myelinated axon waveguide has low attenuation and low dispersion and operates in a narrow bandwidth on the order of 10 nm. We also find that the operating wavelength of the waveguide is almost linearly related to the axon diameter and the number of myelin layers. Each additional layer of the myelin sheath causes the operating wavelength of the myelinated axon waveguide to shift 52.3 nm to the long-wave direction, while an increase in the axon diameter of 1.0 µm causes the operating wavelength to shift 94.5 nm to the short-wave direction. These findings well explain the tendency of the spectral redshift among different species and the spectral blueshift during the aging process of mice. Via the analysis method in this paper, we can predict the wavelength of the propagating biophotons based on the neural structure.
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16
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Norton-Baker B, Rocha MA, Granger-Jones J, Fishman DA, Martin RW. Human γS-Crystallin Resists Unfolding Despite Extensive Chemical Modification from Exposure to Ionizing Radiation. J Phys Chem B 2022; 126:679-690. [PMID: 35021623 PMCID: PMC9977691 DOI: 10.1021/acs.jpcb.1c08157] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ionizing radiation has dramatic effects on living organisms, causing damage to proteins, DNA, and other cellular components. γ radiation produces reactive oxygen species (ROS) that damage biological macromolecules. Protein modification due to interactions with hydroxyl radical is one of the most common deleterious effects of radiation. The human eye lens is particularly vulnerable to the effects of ionizing radiation, as it is metabolically inactive and its proteins are not recycled after early development. Therefore, radiation damage accumulates and eventually can lead to cataract formation. Here we explore the impact of γ radiation on a long-lived structural protein. We exposed the human eye lens protein γS-crystallin (HγS) to high doses of γ radiation and investigated the chemical and structural effects. HγS accumulated many post-translational modifications (PTMs), appearing to gain significant oxidative damage. Biochemical assays suggested that cysteines were affected, with the concentration of free thiol reduced with increasing γ radiation exposure. SDS-PAGE analysis showed that irradiated samples form protein-protein cross-links, including nondisulfide covalent bonds. Tandem mass spectrometry on proteolytic digests of irradiated samples revealed that lysine, methionine, tryptophan, leucine, and cysteine were oxidized. Despite these chemical modifications, HγS remained folded past 10.8 kGy of γ irradiation as evidenced by circular dichroism and intrinsic tryptophan fluorescence spectroscopy.
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Affiliation(s)
- Brenna Norton-Baker
- These authors contributed equally.,Department of Chemistry, University of California, Irvine, CA 92697-2025, USA
| | - Megan A. Rocha
- These authors contributed equally.,Department of Chemistry, University of California, Irvine, CA 92697-2025, USA
| | | | - Dmitry A. Fishman
- Department of Chemistry, University of California, Irvine, CA 92697-2025, USA
| | - Rachel W. Martin
- Department of Chemistry, University of California, Irvine, CA 92697-2025, USA,Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697-3900, USA
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17
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Yin F, Khago D, Martin RW, Butts CT. Bayesian analysis of static light scattering data for globular proteins. PLoS One 2021; 16:e0258429. [PMID: 34648536 PMCID: PMC8516215 DOI: 10.1371/journal.pone.0258429] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2021] [Accepted: 09/28/2021] [Indexed: 11/18/2022] Open
Abstract
Static light scattering is a popular physical chemistry technique that enables calculation of physical attributes such as the radius of gyration and the second virial coefficient for a macromolecule (e.g., a polymer or a protein) in solution. The second virial coefficient is a physical quantity that characterizes the magnitude and sign of pairwise interactions between particles, and hence is related to aggregation propensity, a property of considerable scientific and practical interest. Estimating the second virial coefficient from experimental data is challenging due both to the degree of precision required and the complexity of the error structure involved. In contrast to conventional approaches based on heuristic ordinary least squares estimates, Bayesian inference for the second virial coefficient allows explicit modeling of error processes, incorporation of prior information, and the ability to directly test competing physical models. Here, we introduce a fully Bayesian model for static light scattering experiments on small-particle systems, with joint inference for concentration, index of refraction, oligomer size, and the second virial coefficient. We apply our proposed model to study the aggregation behavior of hen egg-white lysozyme and human γS-crystallin using in-house experimental data. Based on these observations, we also perform a simulation study on the primary drivers of uncertainty in this family of experiments, showing in particular the potential for improved monitoring and control of concentration to aid inference.
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Affiliation(s)
- Fan Yin
- Department of Statistics, University of California at Irvine, Irvine, CA, United States of America
| | - Domarin Khago
- Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, United States of America
| | - Rachel W. Martin
- Departments of Chemistry and Molecular Biology and Biochemistry, University of California at Irvine, Irvine, CA, United States of America
| | - Carter T. Butts
- Departments of Sociology, Statistics, Computer Science and EECS and Institute for Mathematical Behavioral Sciences, University of California at Irvine, Irvine, CA, United States of America
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18
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Sprague-Piercy MA, Rocha MA, Kwok AO, Martin RW. α-Crystallins in the Vertebrate Eye Lens: Complex Oligomers and Molecular Chaperones. Annu Rev Phys Chem 2021; 72:143-163. [PMID: 33321054 PMCID: PMC8062273 DOI: 10.1146/annurev-physchem-090419-121428] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
α-Crystallins are small heat-shock proteins that act as holdase chaperones. In humans, αA-crystallin is expressed only in the eye lens, while αB-crystallin is found in many tissues. α-Crystallins have a central domain flanked by flexible extensions and form dynamic, heterogeneous oligomers. Structural models show that both the C- and N-terminal extensions are important for controlling oligomerization through domain swapping. α-Crystallin prevents aggregation of damaged β- and γ-crystallins by binding to the client protein using a variety of binding modes. α-Crystallin chaperone activity can be compromised by mutation or posttranslational modifications, leading to protein aggregation and cataract. Because of their high solubility and their ability to form large, functional oligomers, α-crystallins are particularly amenable to structure determination by solid-state nuclear magnetic resonance (NMR) and solution NMR, as well as cryo-electron microscopy.
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Affiliation(s)
- Marc A Sprague-Piercy
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697, USA;
| | - Megan A Rocha
- Department of Chemistry, University of California, Irvine, California 92697, USA
| | - Ashley O Kwok
- Department of Chemistry, University of California, Irvine, California 92697, USA
| | - Rachel W Martin
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697, USA;
- Department of Chemistry, University of California, Irvine, California 92697, USA
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19
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Rocha MA, Sprague-Piercy MA, Kwok AO, Roskamp KW, Martin RW. Chemical Properties Determine Solubility and Stability in βγ-Crystallins of the Eye Lens. Chembiochem 2021; 22:1329-1346. [PMID: 33569867 PMCID: PMC8052307 DOI: 10.1002/cbic.202000739] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 12/17/2020] [Indexed: 11/10/2022]
Abstract
βγ-Crystallins are the primary structural and refractive proteins found in the vertebrate eye lens. Because crystallins are not replaced after early eye development, their solubility and stability must be maintained for a lifetime, which is even more remarkable given the high protein concentration in the lens. Aggregation of crystallins caused by mutations or post-translational modifications can reduce crystallin protein stability and alter intermolecular interactions. Common post-translational modifications that can cause age-related cataracts include deamidation, oxidation, and tryptophan derivatization. Metal ion binding can also trigger reduced crystallin solubility through a variety of mechanisms. Interprotein interactions are critical to maintaining lens transparency: crystallins can undergo domain swapping, disulfide bonding, and liquid-liquid phase separation, all of which can cause opacity depending on the context. Important experimental techniques for assessing crystallin conformation in the absence of a high-resolution structure include dye-binding assays, circular dichroism, fluorescence, light scattering, and transition metal FRET.
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Affiliation(s)
- Megan A. Rocha
- Department of Chemistry, University of California, Irvine, 1102 Natural Sciences 2, Irvine, CA 92697-2025 (USA)
| | - Marc A. Sprague-Piercy
- Department of Molecular Biology and Biochemistry, University of California Irvine, 3205 McGaugh Hall, Irvine, CA 92697-2525
| | - Ashley O. Kwok
- Department of Chemistry, University of California, Irvine, 1102 Natural Sciences 2, Irvine, CA 92697-2025 (USA)
| | - Kyle W. Roskamp
- Department of Chemistry, University of California, Irvine, 1102 Natural Sciences 2, Irvine, CA 92697-2025 (USA)
| | - Rachel W. Martin
- Department of Chemistry, University of California, Irvine, 1102 Natural Sciences 2, Irvine, CA 92697-2025 (USA)
- Department of Molecular Biology and Biochemistry, University of California Irvine, 3205 McGaugh Hall, Irvine, CA 92697-2525
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20
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Sarimov RM, Binhi VN, Matveeva TA, Penkov NV, Gudkov SV. Unfolding and Aggregation of Lysozyme under the Combined Action of Dithiothreitol and Guanidine Hydrochloride: Optical Studies. Int J Mol Sci 2021; 22:2710. [PMID: 33800175 PMCID: PMC7962454 DOI: 10.3390/ijms22052710] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 03/02/2021] [Accepted: 03/03/2021] [Indexed: 11/16/2022] Open
Abstract
Using a number of optical techniques (interferometry, dynamic light scattering, and spectroscopy), denaturation of hen egg white lysozyme (HEWL) by treatment with a combination of dithiothreitol (DTT) and guanidine hydrochloride (GdnHCl) has been investigated. The denaturing solutions were selected so that protein denaturation occurred with aggregation (Tris-HCl pH = 8.0, 50 mM, DTT 30 mM) or without aggregation (Tris-HCl pH = 8.0, 50 mM, DTT 30 mM, GdnHCl 6 M) and can be evaluated after 60 min of treatment. It has been found that denatured by solution with 6 M GdnHCl lysozyme completely loses its enzymatic activity after 30 min and the size of the protein molecule increases by 1.5 times, from 3.8 nm to 5.7 nm. Denaturation without of GdnHCl led to aggregation with preserving about 50% of its enzymatic activity. Denaturation of HEWL was examined using interferometry. Previously, it has been shown that protein denaturation that occurs without subsequent aggregation leads to an increase in the refractive index (Δn ~ 4.5 × 10-5). This is most likely due to variations in the HEWL-solvent interface area. By applying modern optical techniques conjointly, it has been possible to obtain information on the nature of time-dependent changes that occur inside a protein and its hydration shell as it undergoes denaturation.
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Affiliation(s)
- Ruslan M. Sarimov
- Prokhorov General Physics Institute of the Russian Academy of Sciences, Vavilov St., 38, 119991 Moscow, Russia; (R.M.S.); (V.N.B.); (T.A.M.)
| | - Vladimir N. Binhi
- Prokhorov General Physics Institute of the Russian Academy of Sciences, Vavilov St., 38, 119991 Moscow, Russia; (R.M.S.); (V.N.B.); (T.A.M.)
| | - Tatiana A. Matveeva
- Prokhorov General Physics Institute of the Russian Academy of Sciences, Vavilov St., 38, 119991 Moscow, Russia; (R.M.S.); (V.N.B.); (T.A.M.)
| | - Nikita V. Penkov
- Institute of Cell Biophysics of the Russian Academy of Sciences, PSCBR RAS, Institutskaya St., 3, Pushchino, 142290 Moscow, Russia;
| | - Sergey V. Gudkov
- Prokhorov General Physics Institute of the Russian Academy of Sciences, Vavilov St., 38, 119991 Moscow, Russia; (R.M.S.); (V.N.B.); (T.A.M.)
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21
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Bonnet H, Coche-Guérente L, Defrancq E, Spinelli N, Van der Heyden A, Dejeu J. Negative SPR Signals during Low Molecular Weight Analyte Recognition. Anal Chem 2021; 93:4134-4140. [PMID: 33577288 DOI: 10.1021/acs.analchem.1c00071] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Surface plasmon resonance (SPR) is a powerful technique for studying biomolecular interactions mainly due to its sensitivity and real-time and label free advantages. While SPR signals are usually positive, only a few studies have reported sensorgrams with negative signals. The aim of the present work is to investigate and to explain the observation of negative SPR signals with the hypothesis that it reflects major changes in ligand conformation resulting from target binding. We demonstrated that these negative unconventional signals were due to the negative complex (ligand/analyte) refractive index increment (RII) deviation from the sum of the RII of the individual entities which counterbalanced the theoretical increase of the signal triggered by the target recognition and the ligand folding. We also found that the conformation change of biomolecules can induce a negative or a positive complex RII deviation depending on its sequence and immobilization mode.
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Affiliation(s)
- H Bonnet
- Université Grenoble Alpes, CNRS, DCM UMR-5250, F-38000 Grenoble, France
| | - L Coche-Guérente
- Université Grenoble Alpes, CNRS, DCM UMR-5250, F-38000 Grenoble, France
| | - E Defrancq
- Université Grenoble Alpes, CNRS, DCM UMR-5250, F-38000 Grenoble, France
| | - N Spinelli
- Université Grenoble Alpes, CNRS, DCM UMR-5250, F-38000 Grenoble, France
| | - A Van der Heyden
- Université Grenoble Alpes, CNRS, DCM UMR-5250, F-38000 Grenoble, France
| | - J Dejeu
- Université Grenoble Alpes, CNRS, DCM UMR-5250, F-38000 Grenoble, France
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22
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Three-dimensional data capture and analysis of intact eye lenses evidences emmetropia-associated changes in epithelial cell organization. Sci Rep 2020; 10:16898. [PMID: 33037268 PMCID: PMC7547080 DOI: 10.1038/s41598-020-73625-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 09/17/2020] [Indexed: 01/16/2023] Open
Abstract
Organ and tissue development are highly coordinated processes; lens growth and functional integration into the eye (emmetropia) is a robust example. An epithelial monolayer covers the anterior hemisphere of the lens, and its organization is the key to lens formation and its optical properties throughout all life stages. To better understand how the epithelium supports lens function, we have developed a novel whole tissue imaging system using conventional confocal light microscopy and a specialized analysis software to produce three-dimensional maps for the epithelium of intact mouse lenses. The open source software package geometrically determines the anterior pole position, the equatorial diameter, and three-dimensional coordinates for each detected cell in the epithelium. The user-friendly cell maps, which retain global lens geometry, allow us to document age-dependent changes in the C57/BL6J mouse lens cell distribution characteristics. We evidence changes in epithelial cell density and distribution in C57/BL6J mice during the establishment of emmetropia between postnatal weeks 4-6. These epithelial changes accompany a previously unknown spheroid to lentoid shape transition of the lens as detected by our analyses. When combined with key findings from previous mouse genetic and cell biological studies, we suggest a cytoskeleton-based mechanism likely underpins these observations.
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23
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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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24
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Lie AL, Pan X, White TW, Donaldson PJ, Vaghefi E. Using the Lens Paradox to Optimize an In Vivo MRI-Based Optical Model of the Aging Human Crystalline Lens. Transl Vis Sci Technol 2020; 9:39. [PMID: 32855885 PMCID: PMC7422912 DOI: 10.1167/tvst.9.8.39] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 06/23/2020] [Indexed: 12/27/2022] Open
Abstract
Purpose To optimize our in vivo magnetic resonance imaging (MRI)-based optical model of the human crystalline lens, developed with a small group of young adults, for a larger cohort spanning a wider age range. Methods Subjective refraction and ocular biometry were measured in 57 healthy adults ages 18 to 86 years who were then scanned using 3T clinical magnetic resonance imaging (MRI) to obtain lens gradient of refractive index (GRIN) and geometry measurements. These parameters were combined with ocular biometric measurements to construct individualized Zemax eye models from which ocular refractive errors and lens powers were determined. Models were optimized by adding an age-dependent factor to the transverse relaxation time (T2)-refractive index (n) calibration to match model-calculated refractive errors with subjective refractions. Results In our subject cohort, subjective refraction shifted toward hyperopia by 0.029 diopter/year as the lens grew larger and developed flatter GRINs with advancing age. Without model optimization, lens powers did not reproduce this clinically observed decrease, the so-called lens paradox, instead increasing by 0.055 diopter/year. However, modifying the T2-n calibration by including an age-dependent factor reproduced the decrease in lens power associated with the lens paradox. Conclusions After accounting for age-related changes in lens physiology in the T2-n calibration, our model was capable of accurately measuring in vivo lens power across a wide age range. This study highlights the need for a better understanding of how age-dependent changes to the GRIN impact the refractive properties of the lens. Translational Relevance MRI is applied clinically to calculate the effect of age-related refractive index changes in the lens paradox.
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Affiliation(s)
- Alyssa L Lie
- School of Optometry and Vision Science, New Zealand National Eye Centre, University of Auckland, Auckland, New Zealand
| | - Xingzheng Pan
- School of Optometry and Vision Science, New Zealand National Eye Centre, University of Auckland, Auckland, New Zealand
| | - Thomas W White
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY, USA
| | - Paul J Donaldson
- Department of Physiology, School of Medical Sciences, New Zealand National Eye Centre, University of Auckland, Auckland, New Zealand
| | - Ehsan Vaghefi
- School of Optometry and Vision Science, New Zealand National Eye Centre, University of Auckland, Auckland, New Zealand
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25
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Roskamp KW, Azim S, Kassier G, Norton-Baker B, Sprague-Piercy MA, Miller RJD, Martin RW. Human γS-Crystallin-Copper Binding Helps Buffer against Aggregation Caused by Oxidative Damage. Biochemistry 2020; 59:2371-2385. [PMID: 32510933 DOI: 10.1021/acs.biochem.0c00293] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Divalent metal cations can play a role in protein aggregation diseases, including cataract. Here we compare the aggregation of human γS-crystallin, a key structural protein of the eye lens, via mutagenesis, ultraviolet light damage, and the addition of metal ions. All three aggregation pathways result in globular, amorphous-looking structures that do not elongate into fibers. We also investigate the molecular mechanism underlying copper(II)-induced aggregation. This work was motivated by the observation that zinc(II)-induced aggregation of γS-crystallin is driven by intermolecular bridging of solvent-accessible cysteine residues, while in contrast, copper(II)-induced aggregation of this protein is exacerbated by the removal of solvent-accessible cysteines via mutation. Here we find that copper(II)-induced aggregation results from a complex mechanism involving multiple interactions with the protein. The initial protein-metal interactions result in the reduction of Cu(II) to Cu(I) with concomitant oxidation of γS-crystallin. In addition to the intermolecular disulfides that represent a starting point for aggregation, intramolecular disulfides also occur in the cysteine loop, a region of the N-terminal domain that was previously found to mediate the early stages of cataract formation. This previously unobserved ability of γS-crystallin to transfer disulfides intramolecularly suggests that it may serve as an oxidation sink for the lens after glutathione levels have become depleted during aging. γS-Crystallin thus serves as the last line of defense against oxidation in the eye lens, a result that underscores the chemical functionality of this protein, which is generally considered to play a purely structural role.
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Affiliation(s)
- Kyle W Roskamp
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
| | - Sana Azim
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, Luruper Chaussee 149, Hamburg 22761, Germany
| | - Günther Kassier
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, Luruper Chaussee 149, Hamburg 22761, Germany
| | - Brenna Norton-Baker
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States.,Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, Luruper Chaussee 149, Hamburg 22761, Germany
| | - Marc A Sprague-Piercy
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697-3900, United States
| | - R J Dwyane Miller
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, Luruper Chaussee 149, Hamburg 22761, Germany.,Departments of Chemistry and Physics, University of Toronto, 80 St. George Street, Toronto, ON M5S 3H6, Canada
| | - Rachel W Martin
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States.,Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697-3900, United States
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26
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Roskamp KW, Paulson CN, Brubaker WD, Martin RW. Function and Aggregation in Structural Eye Lens Crystallins. Acc Chem Res 2020; 53:863-874. [PMID: 32271004 DOI: 10.1021/acs.accounts.0c00014] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Crystallins are transparent, refractive proteins that contribute to the focusing power of the vertebrate eye lens. These proteins are extremely soluble and resist aggregation for decades, even under crowded conditions. Crystallins have evolved to avoid strong interprotein interactions and have unusual hydration properties. Crystallin aggregation resulting from mutation, damage, or aging can lead to cataract, a disease state characterized by opacity of the lens.Different aggregation mechanisms can occur, following multiple pathways and leading to aggregates with varied morphologies. Studies of variant proteins found in individuals with childhood-onset cataract have provided insight into the molecular factors underlying crystallin stability and solubility. Modulation of exposed hydrophobic surface is critical, as is preventing specific intermolecular interactions that could provide nucleation sites for aggregation. Biophysical measurements and structural biology techniques are beginning to provide a detailed picture of how crystallins crowd into the lens, providing high refractivity while avoiding excessively tight binding that would lead to aggregation.Despite the central biological importance of refractivity, relatively few experimental measurements have been made for lens crystallins. Our work and that of others have shown that hydration is important to the high refractive index of crystallin proteins, as are interactions between pairs of aromatic residues and potentially other specific structural features.This Account describes our efforts to understand both the functional and disease states of vertebrate eye lens crystallins, particularly the γ-crystallins. We use a variety of biophysical techniques, notably NMR spectroscopy, to investigate crystallin stability and solubility. In the first section, we describe efforts to understand the relative stability and aggregation propensity of different γS-crystallin variants. The second section focuses on interactions of these proteins with the holdase chaperone αB-crystallin. The third, fourth, and fifth sections explore different modes of aggregation available to crystallin proteins, and the final section highlights the importance of refractive index and the sometimes conflicting demands of selection for refractivity and solubility.
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Affiliation(s)
- Kyle W. Roskamp
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
| | - Carolyn N. Paulson
- Institute for Therapeutics Discovery and Development, University of Minnesota, Minneapolis, Minnesota 55414, United States
| | - William D. Brubaker
- SRI International, 333 Ravenswood Avenue, Menlo Park, California 94025, United States
| | - Rachel W. Martin
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697-3900, United States
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Roskamp KW, Kozlyuk N, Sengupta S, Bierma JC, Martin RW. Divalent Cations and the Divergence of βγ-Crystallin Function. Biochemistry 2019; 58:4505-4518. [PMID: 31647219 DOI: 10.1021/acs.biochem.9b00507] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The βγ-crystallin superfamily contains both β- and γ-crystallins of the vertebrate eye lens and the microbial calcium-binding proteins, all of which are characterized by a common double-Greek key domain structure. The vertebrate βγ-crystallins are long-lived structural proteins that refract light onto the retina. In contrast, the microbial βγ-crystallins bind calcium ions. The βγ-crystallin from the tunicate Ciona intestinalis (Ci-βγ) provides a potential link between these two functions. It binds calcium with high affinity and is found in a light-sensitive sensory organ that is highly enriched in metal ions. Thus, Ci-βγ is valuable for investigating the evolution of the βγ-crystallin fold away from calcium binding and toward stability in the apo form as part of the vertebrate lens. Here, we investigate the effect of Ca2+ and other divalent cations on the stability and aggregation propensity of Ci-βγ and human γS-crystallin (HγS). Beyond Ca2+, Ci-βγ is capable of coordinating Mg2+, Sr2+, Co2+, Mn2+, Ni2+, and Zn2+, although only Sr2+ is bound with comparable affinity to its preferred metal ion. The extent to which the tested divalent cations stabilize Ci-βγ structure correlates strongly with ionic radius. In contrast, none of the tested divalent cations improved the stability of HγS, and some of them induced aggregation. Zn2+, Ni2+, and Co2+ induce aggregation by interacting with cysteine residues, whereas Cu2+-mediated aggregation proceeds via a different binding site.
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Affiliation(s)
- Kyle W Roskamp
- Department of Chemistry , University of California , Irvine , California 92697-2025 , United States
| | - Natalia Kozlyuk
- Department of Chemistry , University of California , Irvine , California 92697-2025 , United States
| | - Suvrajit Sengupta
- Department of Chemistry , University of California , Irvine , California 92697-2025 , United States
| | - Jan C Bierma
- Department of Molecular Biology and Biochemistry , University of California , Irvine , California 92697-3900 , United States
| | - Rachel W Martin
- Department of Chemistry , University of California , Irvine , California 92697-2025 , United States.,Department of Molecular Biology and Biochemistry , University of California , Irvine , California 92697-3900 , United States
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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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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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