1
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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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2
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Vendra VPR, Ostrowski C, Dyba MA, Tarasov SG, Hejtmancik JF. Human γS-Crystallin Mutation F10_Y11delinsLN in the First Greek Key Pair Destabilizes and Impairs Tight Packing Causing Cortical Lamellar Cataract. Int J Mol Sci 2023; 24:14332. [PMID: 37762633 PMCID: PMC10531703 DOI: 10.3390/ijms241814332] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 09/15/2023] [Accepted: 09/17/2023] [Indexed: 09/29/2023] Open
Abstract
Aromatic residues forming tyrosine corners within Greek key motifs are critical for the folding, stability, and order of βγ-crystallins and thus lens transparency. To delineate how a double amino acid substitution in an N-terminal-domain tyrosine corner of the CRYGS mutant p.F10_Y11delinsLN causes juvenile autosomal dominant cortical lamellar cataracts, human γS-crystallin c-DNA was cloned into pET-20b (+) and a p.F10_Y11delinsLN mutant was generated via site-directed mutagenesis, overexpressed, and purified using ion-exchange and size-exclusion chromatography. Structure, stability, and aggregation properties in solution under thermal and chemical stress were determined using spectrofluorimetry and circular dichroism. In benign conditions, the p.F10_Y11delinsLN mutation does not affect the protein backbone but alters its tryptophan microenvironment slightly. The mutant is less stable to thermal and GuHCl-induced stress, undergoing a two-state transition with a midpoint of 60.4 °C (wild type 73.1 °C) under thermal stress and exhibiting a three-state transition with midpoints of 1.25 and 2.59 M GuHCl (wild type: two-state transition with Cm = 2.72 M GuHCl). The mutant self-aggregates upon heating at 60 °C, which is inhibited by α-crystallin and reducing agents. Thus, the F10_Y11delinsLN mutation in human γS-crystallin impairs the protein's tryptophan microenvironment, weakening its stability under thermal and chemical stress, resulting in self-aggregation, lens opacification, and cataract.
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Affiliation(s)
- Venkata Pulla Rao Vendra
- Ophthalmic Molecular Genetics Section, Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA; (V.P.R.V.)
| | - Christian Ostrowski
- Ophthalmic Molecular Genetics Section, Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA; (V.P.R.V.)
| | - Marzena A. Dyba
- Biophysics Resource in the Center for Structural Biology, National Cancer Institute, National Institutes of Health, Frederick, MD 21702, USA; (M.A.D.); (S.G.T.)
| | - Sergey G. Tarasov
- Biophysics Resource in the Center for Structural Biology, National Cancer Institute, National Institutes of Health, Frederick, MD 21702, USA; (M.A.D.); (S.G.T.)
| | - J. Fielding Hejtmancik
- Ophthalmic Molecular Genetics Section, Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA; (V.P.R.V.)
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3
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Patel S, Hosur RV. Replica exchange molecular dynamics simulations reveal self-association sites in M-crystallin caused by mutations provide insights of cataract. Sci Rep 2021; 11:23270. [PMID: 34857812 PMCID: PMC8639718 DOI: 10.1038/s41598-021-02728-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Accepted: 11/09/2021] [Indexed: 11/09/2022] Open
Abstract
Crystallins are ubiquitous, however, prevalence is seen in eye lens. Eye lens crystallins are long-lived and structural intactness is required for maintaining lens transparency and protein solubility. Mutations in crystallins often lead to cataract. In this study, we performed mutations at specific sites of M-crystallin, a close homologue of eye lens crystallin and studied by using replica exchange molecular dynamics simulation with generalized Born implicit solvent model. Mutations were made on the Ca2+ binding residues (K34D and S77D) and in the hydrophobic core (W45R) which is known to cause congenital cataract in homologous γD-crystallin. The chosen mutations caused large motion of the N-terminal Greek key, concomitantly broke the interlocking Greek keys interactions and perturbed the compact core resulting in several folded and partially unfolded states. Partially unfolded states exposed large hydrophobic patches that could act as precursors for self-aggregation. Accumulation of such aggregates is the potential cause of cataract in homologous eye lens crystallins.
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Affiliation(s)
- Sunita Patel
- UM-DAE Centre for Excellence in Basic Sciences, Mumbai University Campus, Vidyanagari, Mumbai, 400098, India.
| | - Ramakrishna V. Hosur
- grid.452882.1UM-DAE Centre for Excellence in Basic Sciences, Mumbai University Campus, Vidyanagari, Mumbai, 400098 India
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4
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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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Vetter CJ, Thorn DC, Wheeler SG, Mundorff CC, Halverson KA, Wales TE, Shinde UP, Engen JR, David LL, Carver JA, Lampi KJ. Cumulative deamidations of the major lens protein γS-crystallin increase its aggregation during unfolding and oxidation. Protein Sci 2020; 29:1945-1963. [PMID: 32697405 PMCID: PMC7454558 DOI: 10.1002/pro.3915] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2020] [Revised: 07/12/2020] [Accepted: 07/20/2020] [Indexed: 01/07/2023]
Abstract
Age-related lens cataract is the major cause of blindness worldwide. The mechanisms whereby crystallins, the predominant lens proteins, assemble into large aggregates that scatter light within the lens, and cause cataract, are poorly understood. Due to the lack of protein turnover in the lens, crystallins are long-lived. A major crystallin, γS, is heavily modified by deamidation, in particular at surface-exposed N14, N76, and N143 to introduce negative charges. In this present study, deamidated γS was mimicked by mutation with aspartate at these sites and the effect on biophysical properties of γS was assessed via dynamic light scattering, chemical and thermal denaturation, hydrogen-deuterium exchange, and susceptibility to disulfide cross-linking. Compared with wild type γS, a small population of each deamidated mutant aggregated rapidly into large, light-scattering species that contributed significantly to the total scattering. Under partially denaturing conditions in guanidine hydrochloride or elevated temperature, deamidation led to more rapid unfolding and aggregation and increased susceptibility to oxidation. The triple mutant was further destabilized, suggesting that the effects of deamidation were cumulative. Molecular dynamics simulations predicted that deamidation augments the conformational dynamics of γS. We suggest that these perturbations disrupt the native disulfide arrangement of γS and promote the formation of disulfide-linked aggregates. The lens-specific chaperone αA-crystallin was poor at preventing the aggregation of the triple mutant. It is concluded that surface deamidations cause minimal structural disruption individually, but cumulatively they progressively destabilize γS-crystallin leading to unfolding and aggregation, as occurs in aged and cataractous lenses.
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Affiliation(s)
- Calvin J. Vetter
- Integrative BiosciencesOregon Health & Science UniversityPortlandOregonUSA
| | - David C. Thorn
- Research School of Chemistry, College of ScienceThe Australian National UniversityActonAustralia
| | - Samuel G. Wheeler
- Integrative BiosciencesOregon Health & Science UniversityPortlandOregonUSA
| | - Charlie C. Mundorff
- Chemical Physiology & BiochemistryOregon Health & Science UniversityPortlandOregonUSA
- Department of Chemistry & Chemical BiologyNortheastern UniversityBostonMassachusettsUSA
| | - Kate A. Halverson
- Chemical Physiology & BiochemistryOregon Health & Science UniversityPortlandOregonUSA
| | - Thomas E. Wales
- Department of Chemistry & Chemical BiologyNortheastern UniversityBostonMassachusettsUSA
| | - Ujwal P. Shinde
- Chemical Physiology & BiochemistryOregon Health & Science UniversityPortlandOregonUSA
| | - John R. Engen
- Department of Chemistry & Chemical BiologyNortheastern UniversityBostonMassachusettsUSA
| | - Larry L. David
- Chemical Physiology & BiochemistryOregon Health & Science UniversityPortlandOregonUSA
| | - John A. Carver
- Research School of Chemistry, College of ScienceThe Australian National UniversityActonAustralia
| | - Kirsten J. Lampi
- Integrative BiosciencesOregon Health & Science UniversityPortlandOregonUSA
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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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7
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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: 35] [Impact Index Per Article: 8.8] [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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8
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Sprague-Piercy MA, Wong E, Roskamp KW, Fakhoury JN, Freites JA, Tobias DJ, Martin RW. Human αB-crystallin discriminates between aggregation-prone and function-preserving variants of a client protein. Biochim Biophys Acta Gen Subj 2019; 1864:129502. [PMID: 31812542 DOI: 10.1016/j.bbagen.2019.129502] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Revised: 11/17/2019] [Accepted: 12/03/2019] [Indexed: 01/01/2023]
Abstract
BACKGROUND The eye lens crystallins are highly soluble proteins that are required to last the lifespan of an organism due to low protein turnover in the lens. Crystallin aggregation leads to formation of light-scattering aggregates known as cataract. The G18V mutation of human γS-crystallin (γS-G18V), which is associated with childhood-onset cataract, causes structural changes throughout the N-terminal domain and increases aggregation propensity. The holdase chaperone protein αB-crystallin does not interact with wild-type γS-crystallin, but does bind its G18V variant. The specific molecular determinants of αB-crystallin binding to client proteins is incompletely charcterized. Here, a new variant of γS, γS-G18A, was created to test the limits of αB-crystallin selectivity. METHODS Molecular dynamics simulations were used to investigate the structure and dynamics of γS-G18A. The overall fold of γS-G18A was assessed by circular dichroism (CD) spectroscopy and intrinsic tryptophan fluorescence. Its thermal unfolding temperature and aggregation propensity were characterized by CD and DLS, respectively. Solution-state NMR was used to characterize interactions between αB-crystallin and γS-G18A. RESULTS γS-G18A exhibits minimal structural changes, but has compromised thermal stability relative to γS-WT. The placement of alanine, rather than valine, at this highly conserved glycine position produces minor changes in hydrophobic surface exposure. However, human αB-crystallin does not bind the G18A variant, in contrast to previous observations for γS-G18V, which aggregates at physiological temperature. CONCLUSIONS αB-crystallin is capable of distinguishing between aggregation-prone and function-preserving variants, and recognizing the transient unfolding or minor conformers that lead to aggregation in the disease-related variant. GENERAL SIGNIFICANCE Human αB-crystallin distinguishes between highly similar variants of a structural crystallin, binding the cataract-related γS-G18V variant, but not the function-preserving γS-G18A variant, which is monomeric at physiological temperature.
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Affiliation(s)
- Marc A Sprague-Piercy
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697, United States of America
| | - Eric Wong
- Department of Chemistry, UC Irvine, Irvine, CA 92697-2025, United States of America
| | - Kyle W Roskamp
- Department of Chemistry, UC Irvine, Irvine, CA 92697-2025, United States of America
| | - Joseph N Fakhoury
- Department of Chemistry, UC Irvine, Irvine, CA 92697-2025, United States of America
| | - J Alfredo Freites
- Department of Chemistry, UC Irvine, Irvine, CA 92697-2025, United States of America
| | - Douglas J Tobias
- Department of Chemistry, UC Irvine, Irvine, CA 92697-2025, United States of America.
| | - Rachel W Martin
- Department of Chemistry, UC Irvine, Irvine, CA 92697-2025, United States of America; Department of Molecular Biology and Biochemistry, UC Irvine, Irvine, CA 92697, United States of America.
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9
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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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10
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Wong EK, Prytkova V, Freites JA, Butts CT, Tobias DJ. Molecular Mechanism of Aggregation of the Cataract-Related γD-Crystallin W42R Variant from Multiscale Atomistic Simulations. Biochemistry 2019; 58:3691-3699. [PMID: 31393108 DOI: 10.1021/acs.biochem.9b00208] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The mechanisms leading to aggregation of the crystallin proteins of the eye lens remain largely unknown. We use atomistic multiscale molecular simulations to model the solution-state conformational dynamics of γD-crystallin and its cataract-related W42R variant at both infinite dilution and physiologically relevant concentrations. We find that the W42R variant assumes a distinct conformation in solution that leaves the Greek key domains of the native fold largely unaltered but lacks the hydrophobic interdomain interface that is key to the stability of wild-type γD-crystallin. At physiologically relevant concentrations, exposed hydrophobic regions in this alternative conformation become primary sites for enhanced interprotein interactions leading to large-scale aggregation.
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Affiliation(s)
- Eric K Wong
- Department of Chemistry , University of California , Irvine , California 92697 , United States
| | - Vera Prytkova
- Department of Chemistry , University of California , Irvine , California 92697 , United States
| | - J Alfredo Freites
- Department of Chemistry , University of California , Irvine , California 92697 , United States
| | - Carter T Butts
- Departments of Sociology, Electrical Engineering and Computer Science, and Statistics , University of California , Irvine , California 92697 , United States
| | - Douglas J Tobias
- Department of Chemistry , University of California , Irvine , California 92697 , United States
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11
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Domínguez-Calva JA, Pérez-Vázquez ML, Serebryany E, King JA, Quintanar L. Mercury-induced aggregation of human lens γ-crystallins reveals a potential role in cataract disease. J Biol Inorg Chem 2018; 23:1105-1118. [DOI: 10.1007/s00775-018-1607-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2018] [Accepted: 08/22/2018] [Indexed: 01/17/2023]
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12
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Wen L, Lyu M, Xiao H, Lan H, Zuo Z, Yin Z. Protein Aggregation and Performance Optimization Based on Microconformational Changes of Aromatic Hydrophobic Regions. Mol Pharm 2018; 15:2257-2267. [PMID: 29694051 DOI: 10.1021/acs.molpharmaceut.8b00115] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Lili Wen
- Key Laboratory of Drug Targeting and Drug Delivery Systems, West China School of Pharmacy, Sichuan University, Chengdu 610041, Sichuan Province, People’s Republic of China
| | - Man Lyu
- Key Laboratory of Drug Targeting and Drug Delivery Systems, West China School of Pharmacy, Sichuan University, Chengdu 610041, Sichuan Province, People’s Republic of China
| | - Huashuai Xiao
- Key Laboratory of Drug Targeting and Drug Delivery Systems, West China School of Pharmacy, Sichuan University, Chengdu 610041, Sichuan Province, People’s Republic of China
| | - Hairong Lan
- Key Laboratory of Drug Targeting and Drug Delivery Systems, West China School of Pharmacy, Sichuan University, Chengdu 610041, Sichuan Province, People’s Republic of China
| | - Zhili Zuo
- State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China
| | - Zongning Yin
- Key Laboratory of Drug Targeting and Drug Delivery Systems, West China School of Pharmacy, Sichuan University, Chengdu 610041, Sichuan Province, People’s Republic of China
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Juvenile-Onset Diabetes and Congenital Cataract: "Double-Gene" Mutations Mimicking a Syndromic Diabetes Presentation. Genes (Basel) 2017; 8:genes8110309. [PMID: 29112131 PMCID: PMC5704222 DOI: 10.3390/genes8110309] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Revised: 10/24/2017] [Accepted: 10/24/2017] [Indexed: 12/16/2022] Open
Abstract
Monogenic forms of diabetes may account for 1–5% of all cases of diabetes, and may occur in the context of syndromic presentations. We investigated the case of a girl affected by insulin-dependent diabetes, diagnosed at 6 years old, associated with congenital cataract. Her consanguineous parents and her four other siblings did not have diabetes or cataract, suggesting a recessive syndrome. Using whole exome sequencing of the affected proband, we identified a heterozygous p.R825Q ABCC8 mutation, located at the exact same amino-acid position as the p.R825W recurring diabetes mutation, hence likely responsible for the diabetes condition, and a homozygous p.G71S mutation in CRYBB1, a gene known to be responsible for congenital cataract. Both mutations were predicted to be damaging and were absent or extremely rare in public databases. Unexpectedly, we found that the mother was also homozygous for the CRYBB1 mutation, and both the mother and one unaffected sibling were heterozygous for the ABCC8 mutation, suggesting incomplete penetrance of both mutations. Incomplete penetrance of ABCC8 mutations is well documented, but this is the first report of an incomplete penetrance of a CRYBB1 mutation, manifesting between susceptible subjects (unaffected mother vs. affected child) and to some extent within the patient herself, who had distinct cataract severities in both eyes. Our finding illustrates the importance of family studies to unmask the role of confounding factors such as double-gene mutations and incomplete penetrance that may mimic monogenic syndromes including in the case of strongly evocative family structure with consanguinity.
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Cataract-associated P23T γD-crystallin retains a native-like fold in amorphous-looking aggregates formed at physiological pH. Nat Commun 2017; 8:15137. [PMID: 28474685 PMCID: PMC5424181 DOI: 10.1038/ncomms15137] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Accepted: 03/02/2017] [Indexed: 01/14/2023] Open
Abstract
Cataracts cause vision loss through the large-scale aggregation of eye lens proteins as a result of ageing or congenital mutations. The development of new treatments is hindered by uncertainty about the nature of the aggregates and their mechanism of formation. We describe the structure and morphology of aggregates formed by the P23T human γD-crystallin mutant associated with congenital cataracts. At physiological pH, the protein forms aggregates that look amorphous and disordered by electron microscopy, reminiscent of the reported formation of amorphous deposits by other crystallin mutants. Surprisingly, solid-state NMR reveals that these amorphous deposits have a high degree of structural homogeneity at the atomic level and that the aggregated protein retains a native-like conformation, with no evidence for large-scale misfolding. Non-physiological destabilizing conditions used in many in vitro aggregation studies are shown to yield qualitatively different, highly misfolded amyloid-like fibrils. Aggregation of eye lens proteins leads to cataracts, a major cause of blindness. Here the authors use solid state NMR to probe the structure of γD-crystallin eye lens proteins aggregates, which are found to retain a native-like conformation.
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Congenital microcornea-cataract syndrome-causing mutation X253R increases βB1-crystallin hydrophobicity to promote aggregate formation. Biochem J 2016; 473:2087-96. [DOI: 10.1042/bcj20160247] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2016] [Accepted: 05/10/2016] [Indexed: 01/12/2023]
Abstract
The high solubility and lifelong stability of crystallins are crucial to the maintenance of lens transparency and optical properties. Numerous crystallin mutations have been linked to congenital cataract, which is one of the leading causes of newborn blindness. Besides cataract, several crystallin mutations have also been linked to syndromes such as congenital microcornea-cataract syndrome (CMCC). However, the molecular mechanism of CMCC caused by crystallin mutations remains elusive. In the present study, we investigated the mechanism of CMCC caused by the X253R mutation in βB1-crystallin. The exogenously expressed X253R proteins were prone to form p62-negative aggregates in HeLa cells, strongly inhibited cell proliferation and induced cell apoptosis. The intracellular X253R aggregates could be successfully redissolved by lanosterol but not cholesterol. The extra 26 residues at the C-terminus of βB1-crystallin introduced by the X253R mutation had little impact on βB1-crystallin structure and stability, but increased βB1-crystallin hydrophobicity and decreased its solubility. Interestingly, the X253R mutant fully abolished the aggregatory propensity of βB1- and βA3/βB1-crystallins at high temperatures, suggesting that X253R was an aggregation-inhibition mutation of β-crystallin homomers and heteromers in dilute solutions. Our results suggest that an increase in hydrophobicity and a decrease in solubility might be responsible for cataractogenesis induced by the X253R mutation, while the cytotoxic effect of X253R aggregates might contribute to the defects in ocular development. Our results also highlight that, at least in some cases, the aggregatory propensity in dilute solutions could not fully mimic the behaviours of mutated proteins in the crowded cytoplasm of the cells.
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Huang KY, Kingsley CN, Sheil R, Cheng CY, Bierma JC, Roskamp KW, Khago D, Martin RW, Han S. Stability of Protein-Specific Hydration Shell on Crowding. J Am Chem Soc 2016; 138:5392-402. [PMID: 27052457 PMCID: PMC7849722 DOI: 10.1021/jacs.6b01989] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We demonstrate that the effect of protein crowding is critically dependent on the stability of the protein's hydration shell, which can dramatically vary between different proteins. In the human eye lens, γS-crystallin (γS-WT) forms a densely packed transparent hydrogel with a high refractive index, making it an ideal system for studying the effects of protein crowding. A single point mutation generates the cataract-related variant γS-G18V, dramatically altering the optical properties of the eye lens. This system offers an opportunity to explore fundamental questions regarding the effect of protein crowding, using γS-WT and γS-G18V: (i) how do the diffusion dynamics of hydration water change as a function of protein crowding?; and (ii) upon hydrogel formation of γS-WT, has a dynamic transition occurred generating a single population of hydration water, or do populations of bulk and hydration water coexist? Using localized spin probes, we separately probe the local translational diffusivity of both surface hydration and interstitial water of γS-WT and γS-G18V in solution. Surprisingly, we find that under the influence of hydrogel formation at highly crowded γS-WT concentrations up to 500 mg/mL, the protein hydration shell remains remarkably dynamic, slowing by less than a factor of 2, if at all, compared to that in dilute protein solutions of ∼5 mg/mL. Upon self-crowding, the population of this robust surface hydration water increases, while a significant bulk-like water population coexists even at ∼500 mg/mL protein concentrations. In contrast, surface water of γS-G18V irreversibly dehydrates with moderate concentration increases or subtle alterations to the solution conditions, demonstrating that the effect of protein crowding is highly dependent on the stability of the protein-specific hydration shell. The core function of γS-crystallin in the eye lens may be precisely its capacity to preserve a robust hydration shell, whose stability is abolished by a single G18V mutation.
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Affiliation(s)
- Kuo-Ying Huang
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106
| | | | - Ryan Sheil
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106
| | - Chi-Yuan Cheng
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106
| | - Jan C. Bierma
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697
| | - Kyle W. Roskamp
- Department of Chemistry, University of California, Irvine, CA 92697
| | - Domarin Khago
- Department of Chemistry, University of California, Irvine, CA 92697
| | - Rachel W. Martin
- Department of Chemistry, University of California, Irvine, CA 92697
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697
| | - Songi Han
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106
- Department of Chemical Engineering, University of California, Santa Barbara, CA 93106
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