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Lin N, Song H, Zhang Y, Chen F, Xu J, Wu W, Tian Q, Luo C, Yao K, Hu L, Chen X. Truncation mutations of CRYGD gene in congenital cataracts cause protein aggregation by disrupting the structural stability of γD-crystallin. Int J Biol Macromol 2024; 277:134292. [PMID: 39084439 DOI: 10.1016/j.ijbiomac.2024.134292] [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: 05/10/2024] [Revised: 07/19/2024] [Accepted: 07/28/2024] [Indexed: 08/02/2024]
Abstract
Congenital cataracts, a prevalent cause of blindness in children, are associated with protein aggregation. γD-crystallin, essential for sustaining lens transparency, exists as a monomer and exhibits excellent structural stability. In our cohort, we identified a nonsense mutation (c.451_452insGACT, p.Y151X) in the CRYGD gene. To explore the effect of truncation mutations on the structure of γD-crystallin, we examined the Y151X and T160RfsX8 mutations, both located in the Greek key motif 4 at the cellular and protein level in this study. Both truncation mutations induced protein misfolding and resulted in the formation of insoluble aggregates when overexpressed in HLE B3 and HEK 293T cells. Moreover, heat, UV irradiation, and oxidative stress increased the proportion of aggregates of mutants in the cells. We next purified γD-crystallin to estimate its structural changes. Truncation mutations led to conformational disruption and a concomitant decrease in protein solubility. Molecular dynamics simulations further demonstrated that partial deletion of the conserved domain within the Greek key motif 4 markedly compromised the overall stability of the protein structure. Finally, co-expression of α-crystallins facilitated the proper folding of truncated mutants and mitigated protein aggregation. In summary, the structural integrity of the Greek key motif 4 in γD-crystallin is crucial for overall structural stability.
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Affiliation(s)
- Ningqin Lin
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China; Institute of Translational Medicine, Zhejiang University School of Medicine, 268 Kaixuan Road, Hangzhou 310020, China
| | - Hang Song
- Department of Ophthalmology, Peking Union Medical College Hospital, No.1 Shuaifuyuan, Beijing 100730, China
| | - Ying Zhang
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China; Institute of Translational Medicine, Zhejiang University School of Medicine, 268 Kaixuan Road, Hangzhou 310020, China
| | - Fanrui Chen
- Gansu Key Laboratory of Biomonitoring and Bioremediation for Environmental Pollution, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
| | - Jingjie Xu
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China
| | - Wei Wu
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China
| | - Qing Tian
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China; Institute of Translational Medicine, Zhejiang University School of Medicine, 268 Kaixuan Road, Hangzhou 310020, China
| | - Chenqi Luo
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China
| | - Ke Yao
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China
| | - Lidan Hu
- The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, 3333 Binsheng Road, Hangzhou 310052, China.
| | - Xiangjun Chen
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China; Institute of Translational Medicine, Zhejiang University School of Medicine, 268 Kaixuan Road, Hangzhou 310020, China.
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Diessner EM, Takahashi GR, Butts CT, Martin RW. Comparative analysis of thermal adaptations of extremophilic prolyl oligopeptidases. Biophys J 2024; 123:3143-3162. [PMID: 39014897 PMCID: PMC11427779 DOI: 10.1016/j.bpj.2024.07.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Revised: 05/14/2024] [Accepted: 07/10/2024] [Indexed: 07/18/2024] Open
Abstract
Prolyl oligopeptidases from psychrophilic, mesophilic, and thermophilic organisms found in a range of natural environments are studied using a combination of protein structure prediction, atomistic molecular dynamics, and trajectory analysis to determine how the S9 protease family adapts to extreme thermal conditions. We compare our results with hypotheses from the literature regarding structural adaptations that allow proteins to maintain structure and function at extreme temperatures, and we find that, in the case of prolyl oligopeptidases, only a subset of proposed adaptations are employed for maintaining stability. The catalytic and propeller domains are highly structured, limiting the range of mutations that can be made to enhance hydrophobicity or form disulfide bonds without disrupting the formation of necessary secondary structure. Rather, we observe a pattern in which overall prevalence of bound interactions (salt bridges and hydrogen bonds) is conserved by using increasing numbers of increasingly short-lived interactions as temperature increases. This suggests a role for an entropic rather than energetic strategy for thermal adaptation in this protein family.
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Affiliation(s)
| | - Gemma R Takahashi
- Department of Molecular Biology & Biochemistry, University of California, Irvine, Irvine, California
| | - Carter T Butts
- Departments of Sociology, Statistics, Computer Science, and EECS, University of California, Irvine, Irvine, California.
| | - Rachel W Martin
- Department of Chemistry, University of California, Irvine, Irvine, California; Department of Molecular Biology & Biochemistry, University of California, Irvine, Irvine, California.
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3
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Sun J, Morishima K, Inoue R, Sugiyama M, Takata T. Characterization of βB2-crystallin tryptophan mutants reveals two different folding states in solution. Protein Sci 2024; 33:e5092. [PMID: 38924206 PMCID: PMC11201810 DOI: 10.1002/pro.5092] [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: 03/30/2024] [Revised: 06/07/2024] [Accepted: 06/11/2024] [Indexed: 06/28/2024]
Abstract
Conserved tryptophan residues are critical for the structure and the stability of β/γ-crystallin in the lenses of vertebrates. During aging, in which the lenses are continuously exposed to ultraviolet irradiation and other environmental stresses, oxidation of tryptophan residues in β/γ-crystallin is triggered and impacts the lens proteins to varying degrees. Kynurenine derivatives, formed by oxidation of tryptophan, accumulate, resulting in destabilization and insolubilization of β/γ-crystallin, which correlates with age-related cataract formation. To understand the contribution of tryptophan modification on the structure and stability of human βB2-crystallin, five tryptophan residues were mutated to phenylalanine considering its similarity in structure and hydrophilicity to kynurenine. Among all mutants, W59F and W151F altered the stability and homo-oligomerization of βB2-crystallin-W59F promoted tetramerization whereas W151F blocked oligomerization. Most W59F dimers transformed into tetramer in a month, and the separated dimer and tetramer of W59F demonstrated different structures and hydrophobicity, implying that the biochemical properties of βB2-crystallin vary over time. By using SAXS, we found that the dimer of βB2-crystallin in solution resembled the lattice βB1-crystallin dimer (face-en-face), whereas the tetramer of βB2-crystallin in solution resembled its lattice tetramer (domain-swapped). Our results suggest that homo-oligomerization of βB2-crystallin includes potential inter-subunit reactions, such as dissociation, unfolding, and re-formation of the dimers into a tetramer in solution. The W>F mutants are useful in studying different folding states of βB2-crystallin in lens.
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Affiliation(s)
- Jiayue Sun
- Department of Chemistry, Graduate School of ScienceKyoto UniversityKyotoJapan
| | - Ken Morishima
- Institute for Integrated Radiation and Nuclear ScienceKyoto UniversityOsakaJapan
| | - Rintaro Inoue
- Institute for Integrated Radiation and Nuclear ScienceKyoto UniversityOsakaJapan
| | - Masaaki Sugiyama
- Institute for Integrated Radiation and Nuclear ScienceKyoto UniversityOsakaJapan
| | - Takumi Takata
- Institute for Integrated Radiation and Nuclear ScienceKyoto UniversityOsakaJapan
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4
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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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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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Ghosh D, Sojitra KA, Biswas A, Agarwal M, Radhakrishna M. Effect of mutations on the folding and stability of γD-crystallin protein. J Biomol Struct Dyn 2023:1-15. [PMID: 37830785 DOI: 10.1080/07391102.2023.2266768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Accepted: 09/25/2023] [Indexed: 10/14/2023]
Abstract
Interprotein interactions between the partially unfolded states of γD-crystallin (γD-crys) protein are known to cause cataracts. Therefore, understanding the unfolding pathways of native γD-crys is extremely crucial to delineate their aggregation mechanism. In this study, we have performed extensive all-atom Molecular Dynamics simulations with explicit solvent to understand the role of the critical residues that drive the stability of the motifs and domains of γD-crys in its wild type and mutant forms. Our findings show that while the individual motifs of wild type are not stable in the native form, the individual domains remain structurally stable at 425K. This enhanced stability of the domain was attributed to the hydrophobic interactions between the motifs. Single and double point mutations of the domains with negatively charged aspartic and glutamic acid amino acid residues (I3E, W42D, W42E, I3D/W42D, I3E/W42E, and L92D/W157D) decreases the structural stability, leading to unfolding of individual domains of γD-crys. We believe that our study sheds light on the weakest links of γD-crys, along with the role of interactions stabilizing the domains. Further, this study bolsters and provides a better understanding of the domain swapping mechanism of aggregation of γD-crys.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Deepshikha Ghosh
- Department of Biological Sciences and Engineering, Indian Institute of Technology (IIT), Gandhinagar, Palaj, Gujarat, India
| | - Kandarp Ashokbhai Sojitra
- Replace with:Department of Chemical Engineering, Indian Institute of Technology (IIT) Gandhinagar, Palaj, Gujarat, India
| | - Anushka Biswas
- Replace with:Department of Chemical Engineering, Indian Institute of Technology (IIT) Gandhinagar, Palaj, Gujarat, India
| | - Manish Agarwal
- Computer Services Centre, Indian Institute of Technology (IIT) Delhi, Hauz Khas, New Delhi, Delhi
| | - Mithun Radhakrishna
- Replace with:Department of Chemical Engineering, Indian Institute of Technology (IIT) Gandhinagar, Palaj, Gujarat, India
- Center for Biomedical Engineering, Indian Institute of Technology (IIT) Gandhinagar, Palaj, Gujarat, India
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7
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Rodríguez-Meza O, Palomino-Vizcaino G, Quintanar L, Costas M. Mercury ions impact the kinetic and thermal stabilities of human lens γ-crystallins via direct metal-protein interactions. J Inorg Biochem 2023; 242:112159. [PMID: 36827733 DOI: 10.1016/j.jinorgbio.2023.112159] [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: 10/02/2022] [Revised: 02/06/2023] [Accepted: 02/06/2023] [Indexed: 02/17/2023]
Abstract
Loss of metal homeostasis may be involved in several age-related diseases, such as cataracts. Cataracts are caused by the aggregation of lens proteins into light-scattering high molecular weight complexes that impair vision. Environmental exposure to heavy metals, such as mercury, is a risk factor for cataract development. Indeed, mercury ions induce the non-amyloid aggregation of human γC- and γS crystallins, while human γD-crystallin is not sensitive to this metal. Using Differential Scanning Calorimetry (DSC), we evaluate the impact of mercury ions on the kinetic stability of the three most abundant human γ-crystallins. The metal/crystallin interactions were characterized using Isothermal Titration Calorimetry (ITC). Human γD-crystallins exhibited kinetic stabilization due to the presence of mercury ions, despite its thermal stability being decreased. In contrast, human γC- and γS-crystallins are both, thermally and kinetically destabilized by this metal, consistent with their sensitivity to mercury-induced aggregation. The interaction of human γ-crystallins with mercury ions is highly exothermic and complex, since the protein interacts with the metal at more than three sites. The isolated domains of human γ-D and its variant with the H22Q mutation were also studied, revealing the importance of these regions in the mercury-induced stabilization by a direct metal-protein interaction.
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Affiliation(s)
- Oscar Rodríguez-Meza
- Laboratorio de Biofisicoquímica, Departamento de Fisicoquímica, Facultad de Química, Universidad Nacional Autónoma de México, CdMx 04510, Mexico
| | | | - Liliana Quintanar
- Departamento de Química, Centro de Investigación y Estudios Avanzados (Cinvestav), CdMx 07360, Mexico
| | - Miguel Costas
- Laboratorio de Biofisicoquímica, Departamento de Fisicoquímica, Facultad de Química, Universidad Nacional Autónoma de México, CdMx 04510, Mexico.
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8
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Islam S, Do M, Frank BS, Hom GL, Wheeler S, Fujioka H, Wang B, Minocha G, Sell DR, Fan X, Lampi KJ, Monnier VM. α-Crystallin chaperone mimetic drugs inhibit lens γ-crystallin aggregation: potential role for cataract prevention. J Biol Chem 2022; 298:102417. [PMID: 36037967 PMCID: PMC9525908 DOI: 10.1016/j.jbc.2022.102417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Revised: 08/15/2022] [Accepted: 08/16/2022] [Indexed: 11/29/2022] Open
Abstract
Γ-Crystallins play a major role in age-related lens transparency. Their destabilization by mutations and physical chemical insults are associated with cataract formation. Therefore, drugs that increase their stability should have anticataract properties. To this end, we screened 2560 Federal Drug Agency–approved drugs and natural compounds for their ability to suppress or worsen H2O2 and/or heat-mediated aggregation of bovine γ-crystallins. The top two drugs, closantel (C), an antihelminthic drug, and gambogic acid (G), a xanthonoid, attenuated thermal-induced protein unfolding and aggregation as shown by turbidimetry fluorescence spectroscopy dynamic light scattering and electron microscopy of human or mouse recombinant crystallins. Furthermore, binding studies using fluorescence inhibition and hydrophobic pocket–binding molecule bis-8-anilino-1-naphthalene sulfonic acid revealed static binding of C and G to hydrophobic sites with medium-to-low affinity. Molecular docking to HγD and other γ-crystallins revealed two binding sites, one in the “NC pocket” (residues 50–150) of HγD and one spanning the “NC tail” (residues 56–61 to 168–174 in the C-terminal domain). Multiple binding sites overlap with those of the protective mini αA-crystallin chaperone MAC peptide. Mechanistic studies using bis-8-anilino-1-naphthalene sulfonic acid as a proxy drug showed that it bound to MAC sites, improved Tm of both H2O2 oxidized and native human gamma D, and suppressed turbidity of oxidized HγD, most likely by trapping exposed hydrophobic sites. The extent to which these drugs act as α-crystallin mimetics and reduce cataract progression remains to be demonstrated. This study provides initial insights into binding properties of C and G to γ-crystallins.
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Affiliation(s)
- Sidra Islam
- Dept of Pathology and Biochemistry, Case Western Reserve University, Cleveland, OH 44106
| | - Michael Do
- Dept of Pathology and Biochemistry, Case Western Reserve University, Cleveland, OH 44106
| | - Brett S Frank
- Dept of Pathology and Biochemistry, Case Western Reserve University, Cleveland, OH 44106
| | - Grant L Hom
- Dept of Pathology and Biochemistry, Case Western Reserve University, Cleveland, OH 44106
| | - Samuel Wheeler
- Dept of Integrative Biosciences, Oregon Health & Sciences University, Portland, OR 97239
| | - Hisashi Fujioka
- Cryo-EM Core Facility, School of Medicine, Case Western Reserve University, Case Western Reserve University, Cleveland, OH 44016
| | - Benlian Wang
- Center for Proteomics and Bioinformatics, Dept of Nutrition, Case Western Reserve University, Cleveland, OH 44106
| | - Geeta Minocha
- Dept of Pathology and Biochemistry, Case Western Reserve University, Cleveland, OH 44106
| | - David R Sell
- Dept of Pathology and Biochemistry, Case Western Reserve University, Cleveland, OH 44106
| | - Xingjun Fan
- Dept of Cell Biology and Anatomy, Augusta University, Georgia, GA 30912
| | - Kirsten J Lampi
- Dept of Integrative Biosciences, Oregon Health & Sciences University, Portland, OR 97239
| | - Vincent M Monnier
- Dept of Pathology and Biochemistry, Case Western Reserve University, Cleveland, OH 44106; Dept of Biochemistry, Case Western Reserve University, Cleveland OH 44106.
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Serebryany E, Chowdhury S, Woods CN, Thorn DC, Watson NE, McClelland AA, Klevit RE, Shakhnovich EI. A native chemical chaperone in the human eye lens. eLife 2022; 11:76923. [PMID: 35723573 PMCID: PMC9246369 DOI: 10.7554/elife.76923] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Accepted: 06/13/2022] [Indexed: 12/02/2022] Open
Abstract
Cataract is one of the most prevalent protein aggregation disorders and still the most common cause of vision loss worldwide. The metabolically quiescent core region of the human lens lacks cellular or protein turnover; it has therefore evolved remarkable mechanisms to resist light-scattering protein aggregation for a lifetime. We now report that one such mechanism involves an unusually abundant lens metabolite, myo-inositol, suppressing aggregation of lens crystallins. We quantified aggregation suppression using our previously well-characterized in vitro aggregation assays of oxidation-mimicking human γD-crystallin variants and investigated myo-inositol’s molecular mechanism of action using solution NMR, negative-stain TEM, differential scanning fluorometry, thermal scanning Raman spectroscopy, turbidimetry in redox buffers, and free thiol quantitation. Unlike many known chemical chaperones, myo-inositol’s primary target was not the native, unfolded, or final aggregated states of the protein; rather, we propose that it was the rate-limiting bimolecular step on the aggregation pathway. Given recent metabolomic evidence that it is severely depleted in human cataractous lenses compared to age-matched controls, we suggest that maintaining or restoring healthy levels of myo-inositol in the lens may be a simple, safe, and globally accessible strategy to prevent or delay lens opacification due to age-onset cataract.
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Affiliation(s)
- Eugene Serebryany
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States
| | - Sourav Chowdhury
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States
| | - Christopher N Woods
- Department of Biochemistry, University of Washington, Seattle, United States
| | - David C Thorn
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States
| | - Nicki E Watson
- Center for Nanoscale Systems, Harvard University, Cambridge, United States
| | | | - Rachel E Klevit
- Department of Biochemistry, University of Washington, Seattle, United States
| | - Eugene I Shakhnovich
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States
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10
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Hsueh SS, Wang SS(S, Chen SH, Wang CL, Wu W(J, Lin TH. Insights to Human γD-Crystallin Unfolding by NMR Spectroscopy and Molecular Dynamics Simulations. Int J Mol Sci 2022; 23:ijms23031591. [PMID: 35163513 PMCID: PMC8836049 DOI: 10.3390/ijms23031591] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Revised: 01/13/2022] [Accepted: 01/19/2022] [Indexed: 11/16/2022] Open
Abstract
Human γD-crystallin (HGDC) is an abundant lens protein residing in the nucleus of the human lens. Aggregation of this and other structural proteins within the lens leads to the development of cataract. Much has been explored on the stability and aggregation of HGDC and where detailed investigation at the atomic resolution was needed, the X-ray structure was used as an initial starting conformer for molecular modeling. In this study, we implemented NMR-solution HGDC structures as starting conformers for molecular dynamics simulations to provide the missing pieces of the puzzle on the very early stages of HGDC unfolding leading up to the domain swap theories proposed by past studies. The high-resolution details of the conformational dynamics also revealed additional insights to possible early intervention for cataractogenesis.
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Affiliation(s)
- Shu-Shun Hsueh
- Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan; (S.-S.H.); (S.-S.W.); (S.-H.C.)
| | - S.-S. (Steven) Wang
- Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan; (S.-S.H.); (S.-S.W.); (S.-H.C.)
| | - Shu-Han Chen
- Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan; (S.-S.H.); (S.-S.W.); (S.-H.C.)
| | - Chia-Lin Wang
- Laboratory of Nuclear Magnetic Resonance, Medical Research Department, Taipei Veterans General Hospital, Taipei 11217, Taiwan;
| | - W. (Josephine) Wu
- Department of Optometry, Yuanpei University of Medical Technology, Hsinchu City 30015, Taiwan
- Correspondence: (J.W.W.); (T.-H.L.); Tel.: +886-3-538-1183 (ext. 8608) (W.W.); +886-2-28712121 (ext. 2703) (T.-H.L.)
| | - Ta-Hsien Lin
- Laboratory of Nuclear Magnetic Resonance, Medical Research Department, Taipei Veterans General Hospital, Taipei 11217, Taiwan;
- Institute of Biochemistry and Molecular Biology, National Yang Ming Chiao Tung University, Taipei 11221, Taiwan
- Correspondence: (J.W.W.); (T.-H.L.); Tel.: +886-3-538-1183 (ext. 8608) (W.W.); +886-2-28712121 (ext. 2703) (T.-H.L.)
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11
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Hsueh SS, Lu JH, Wu JW, Lin TH, Wang SSS. Protection of human γD-crystallin protein from ultraviolet C-induced aggregation by ortho-vanillin. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2021; 261:120023. [PMID: 34098480 DOI: 10.1016/j.saa.2021.120023] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 05/20/2021] [Accepted: 05/24/2021] [Indexed: 06/12/2023]
Abstract
Cataract is known as one of the leading causes of vision impairment worldwide. While the detailed mechanism of cataratogenesis remains unclear, cataract is believed to be correlated with the aggregation and/or misfolding of human ocular lens proteins called crystallins. A 173-residue structural protein human γD-crystallin is a major γ-crystallin protein in the human eye lens and associated with the development of juvenile and mature-onset cataracts. This work is aimed at investigating the effect of a small molecule, e.g., ortho-vanillin, on human γD-crystallin aggregation upon exposure to ultraviolet-C irradiation. According to the findings of right-angle light scattering, transmission electron microscopy, and gel electrophoresis, ortho-vanillin was demonstrated to dose-dependently suppress ultraviolet-C-triggered aggregation of human γD-crystallin. Results from the synchronous fluorescence spectroscopy, tryptophan fluorescence quenching, and molecular docking studies revealed the structural change of γD-crystallin induced by the interaction/binding between ortho-vanillin and protein. We believe the outcome from this work may contribute to the development of potential therapeutics for cataract.
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Affiliation(s)
- Shu-Shun Hsueh
- Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan
| | - Jian-Hong Lu
- Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan
| | - Josephine W Wu
- Department of Optometry, Yuanpei University of Medical Technology, Hsinchu City 30015, Taiwan.
| | - Ta-Hsien Lin
- Basic Research Division, Medical Research Department, Taipei Veterans General Hospital, Taipei 11217, Taiwan; Institute of Biochemistry and Molecular Biology, National Yang Ming Chiao Tung University, Taipei 11221, Taiwan.
| | - Steven S-S Wang
- Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan.
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12
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Serebryany E, Thorn DC, Quintanar L. Redox chemistry of lens crystallins: A system of cysteines. Exp Eye Res 2021; 211:108707. [PMID: 34332989 PMCID: PMC8511183 DOI: 10.1016/j.exer.2021.108707] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Revised: 07/09/2021] [Accepted: 07/23/2021] [Indexed: 11/28/2022]
Abstract
The nuclear region of the lens is metabolically quiescent, but it is far from inert chemically. Without cellular renewal and with decades of environmental exposures, the lens proteome, lipidome, and metabolome change. The lens crystallins have evolved exquisite mechanisms for resisting, slowing, adapting to, and perhaps even harnessing the effects of these cumulative chemical modifications to minimize the amount of light-scattering aggregation in the lens over a lifetime. Redox chemistry is a major factor in these damages and mitigating adaptations, and as such, it is likely to be a key component of any successful therapeutic strategy for preserving or rescuing lens transparency, and perhaps flexibility, during aging. Protein redox chemistry is typically mediated by Cys residues. This review will therefore focus primarily on the Cys-rich γ-crystallins of the human lens, taking care to extend these findings to the β- and α-crystallins where pertinent.
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Affiliation(s)
- Eugene Serebryany
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA.
| | - David C Thorn
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
| | - Liliana Quintanar
- Department of Chemistry, Centro de Investigación y de Estudios Avanzados (Cinvestav), Mexico City, Mexico
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13
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Song J. Adenosine triphosphate energy-independently controls protein homeostasis with unique structure and diverse mechanisms. Protein Sci 2021; 30:1277-1293. [PMID: 33829608 PMCID: PMC8197423 DOI: 10.1002/pro.4079] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 03/30/2021] [Accepted: 04/02/2021] [Indexed: 02/06/2023]
Abstract
Proteins function in the crowded cellular environments with high salt concentrations, thus facing tremendous challenges of misfolding/aggregation which represents a pathological hallmark of aging and an increasing spectrum of human diseases. Recently, intrinsically disordered regions (IDRs) were recognized to drive liquid-liquid phase separation (LLPS), a common principle for organizing cellular membraneless organelles (MLOs). ATP, the universal energy currency for all living cells, mysteriously has concentrations of 2-12 mM, much higher than required for its previously-known functions. Only recently, ATP was decoded to behave as a biological hydrotrope to inhibit protein LLPS and aggregation at mM. We further revealed that ATP also acts as a bivalent binder, which not only biphasically modulates LLPS driven by IDRs of human and viral proteins, but also bind to the conserved nucleic-acid-binding surfaces of the folded proteins. Most unexpectedly, ATP appears to act as a hydration mediator to antagonize the crowding-induced destabilization as well as to enhance folding of proteins without significant binding. Here, this review focuses on summarizing the results of these biophysical studies and discussing their implications in an evolutionary context. By linking triphosphate with unique hydration property to adenosine, ATP appears to couple the ability for establishing hydrophobic, π-π, π-cation and electrostatic interactions to the capacity in mediating hydration of proteins, which is at the heart of folding, dynamics, stability, phase separation and aggregation. Consequently, ATP acquired a category of functions at ~mM to energy-independently control protein homeostasis with diverse mechanisms, thus implying a link between cellular ATP concentrations and protein-aggregation diseases.
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Affiliation(s)
- Jianxing Song
- Department of Biological Sciences, Faculty of ScienceNational University of SingaporeSingaporeSingapore
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14
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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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15
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Mondal B, Nagesh J, Reddy G. Double Domain Swapping in Human γC and γD Crystallin Drives Early Stages of Aggregation. J Phys Chem B 2021; 125:1705-1715. [PMID: 33566611 DOI: 10.1021/acs.jpcb.0c07833] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Human γD (HγD) and γC (HγC) are two-domain crystallin (Crys) proteins expressed in the nucleus of the eye lens. Structural perturbations in the protein often trigger aggregation, which eventually leads to cataract. To decipher the underlying molecular mechanism, it is important to characterize the partially unfolded conformations, which are aggregation-prone. Using a coarse grained protein model and molecular dynamics simulations, we studied the role of on-pathway folding intermediates in the early stages of aggregation. The multidimensional free energy surface revealed at least three different folding pathways with the population of partially structured intermediates. The two dominant pathways confirm sequential folding of the N-terminal [Ntd] and the C-terminal domains [Ctd], while the third, least favored, pathway involves intermediates where both the domains are partially folded. A native-like intermediate (I*), featuring the folded domains and disrupted interdomain contacts, gets populated in all three pathways. I* forms domain swapped dimers by swapping the entire Ntds and Ctds with other monomers. Population of such oligomers can explain the increased resistance to unfolding resulting in hysteresis observed in the folding experiments of HγD Crys. An ensemble of double domain swapped dimers are also formed during refolding, where intermediates consisting of partially folded Ntds and Ctds swap secondary structures with other monomers. The double domain swapping model presented in our study provides structural insights into the early events of aggregation in Crys proteins and identifies the key secondary structural swapping elements, where introducing mutations will aid in regulating the overall aggregation propensity.
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Affiliation(s)
- Balaka Mondal
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka, India 560012
| | - Jayashree Nagesh
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka, India 560012
| | - Govardhan Reddy
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka, India 560012
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16
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Velasco-Bolom JL, Domínguez L. Exploring the folding process of human βB2-crystallin using multiscale molecular dynamics and the Markov state model. Phys Chem Chem Phys 2021; 22:26753-26763. [PMID: 33205789 DOI: 10.1039/d0cp04136j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Adequate knowledge of protein conformations is crucial for understanding their function and their association properties with other proteins. The cataract disease is correlated with conformational changes in key proteins called crystallins. These changes are due to mutations or post-translational modifications that may lead to protein unfolding, and thus the formation of aggregate states. Human βB2-crystallin (HβB2C) is found in high proportion in the eye lens, and its mutations are related to some cataracts. HβB2C also associates into dimers, tetramers, and other higher-order supramolecular complexes. However, it is the only protein of the βγ-crystallin family that has been found in an extended conformation. Therefore, we hypothesize that the extended conformation is not energetically favourable and that HβB2C may adopt a closed (completely folded) conformation, similar to the other members of the βγ-crystallin family. To corroborate this hypothesis, we performed extensive molecular dynamics simulations of HβB2C in its monomeric and dimeric conformations, using all-atom and coarse-grained scales. We employed Markov state model (MSM) analysis to characterize the conformational and kinetically relevant states in the folding process of monomeric HβB2C. The MSM analysis clearly shows that HβB2C adopts a completely folded structure, and this conformation is the most kinetically and energetically favourable one. In contrast, the extended conformations are kinetically unstable and energetically unfavourable. Our MSM analysis also reveals a key metastable state, which is particularly interesting because it is from this state that the folded state is reached. The folded state is stabilized by the formation of two salt bridges between the residue-pairs E74-R187 and R97-E166 and the two hydrophobic residue-pairs V59-L164 and V72-V151. Furthermore, free energy surface (FES) analysis revealed that the HβB2C dimer with both monomers in a closed conformation (face-en-face dimer) is energetically more stable than the domain-swapped dimer (crystallographic structure). The results presented in this report shed light on the molecular details of the folding mechanism of HβB2C in an aqueous environment and may contribute to interpreting different experimental findings. Finally, a detailed knowledge of HβB2C folding may be key to the rational design of potential molecules to treat cataract disease.
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Affiliation(s)
- José-Luis Velasco-Bolom
- Facultad de Química, Departamento de Fisicoquímica, Universidad Nacional Autónoma de México, Mexico City, 04510, Mexico.
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17
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Wang KJ, Liao XY, Lin K, Xi YB, Wang S, Wan XH, Yan YB. A novel F30S mutation in γS-crystallin causes autosomal dominant congenital nuclear cataract by increasing susceptibility to stresses. Int J Biol Macromol 2021; 172:475-482. [PMID: 33454329 DOI: 10.1016/j.ijbiomac.2021.01.079] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2020] [Revised: 01/03/2021] [Accepted: 01/12/2021] [Indexed: 01/14/2023]
Abstract
Despite of increasingly accumulated genetic variations of autosomal dominant congenital cataracts (ADCC), the causative genes of many ADCC patients remains unknown. In this research, we identified a novel F30S mutation in γS-crystallin from a three-generation Chinese family with ADCC. The patients possessing the F30S mutation exhibited nuclear cataract phenotype. The potential molecular mechanism underlying ADCC by the F30S mutation was investigated by comparing the structural features, stability and aggregatory potency of the mutated protein with the wild type protein. Spectroscopic experiments indicated that the F30S mutation did not affect γS-crystallin secondary structure compositions, but modified the microenvironments around aromatic side-chains. Thermal and chemical denaturation studies indicated that the mutation destabilized the protein and increased its aggregatory potency. The mutation altered the two-state unfolding of γS-crystallin to a three-state unfolding with the accumulation of an unfolding intermediate. The almost identical values in the changes of Gibbs free energies for transitions from the native state to intermediate and from the intermediate to unfolded state suggested that the mutation probably disrupted the cooperativity between the two domains during unfolding. Our results expand the genetic variation map of ADCC and provide novel insights into the molecular mechanism underlying ADCC caused by mutations in β/γ-crystallins.
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Affiliation(s)
- Kai-Jie Wang
- Beijing Tongren Eye Center, Beijing Ophthalmology & Visual Sciences Key Lab, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China
| | - Xiao-Yan Liao
- State Key Laboratory of Membrane Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Kunxia Lin
- Ophthalmology Department, Fujian Provincial Hospital, Fuzhou, 350001, China
| | - Yi-Bo Xi
- State Key Laboratory of Membrane Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Sha Wang
- State Key Laboratory of Membrane Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Xiu-Hua Wan
- Beijing Tongren Eye Center, Beijing Ophthalmology & Visual Sciences Key Lab, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China.
| | - Yong-Bin Yan
- State Key Laboratory of Membrane Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China.
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18
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Cataract-causing mutations L45P and Y46D promote γC-crystallin aggregation by disturbing hydrogen bonds network in the second Greek key motif. Int J Biol Macromol 2020; 167:470-478. [PMID: 33278449 DOI: 10.1016/j.ijbiomac.2020.11.158] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 10/23/2020] [Accepted: 11/23/2020] [Indexed: 02/07/2023]
Abstract
Congenital cataracts caused by genetic disorders are the primary cause of child blindness across the globe. In this work, we investigated the underlying molecular mechanism of two mutations, L45P and Y46D of γC-crystallin in two Chinese families causing nuclear congenital cataracts. Spectroscopic experiments were performed to determine structural differences between the wild-type (WT) and the L45P or Y46D mutant of γC-crystallin, and the structural stabilities of the WT and mutant proteins were measured under environmental stress (ultraviolet irradiation, pH disorders, oxidative stress, or chemical denaturation). The L45P and Y46D mutants had lower protein solubility and more hydrophobic residues exposed, making them prone to aggregation under environmental stress. The dynamic molecular simulation revealed that the L45P and Y46D mutations destabilized γC-crystallin by altering the hydrogen bonds network around the Trp residues in the second Greek key motif. In summary, L45P and Y46D mutants of γC-crystallin caused more hydrophobic residues to be solvent-exposed, lowered the solubility of γC-crystallin, and increased aggregation propensity under environmental stress. These might be the pathogenesis of γC-crystallin L45P and Y46D mutants related to congenital cataract.
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19
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Berry V, Ionides A, Pontikos N, Georgiou M, Yu J, Ocaka LA, Moore AT, Quinlan RA, Michaelides M. The genetic landscape of crystallins in congenital cataract. Orphanet J Rare Dis 2020; 15:333. [PMID: 33243271 PMCID: PMC7691105 DOI: 10.1186/s13023-020-01613-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Accepted: 11/10/2020] [Indexed: 02/01/2023] Open
Abstract
Background The crystalline lens is mainly composed of a large family of soluble proteins called the crystallins, which are responsible for its development, growth, transparency and refractive index. Disease-causing sequence variants in the crystallins are responsible for nearly 50% of all non-syndromic inherited congenital cataracts, as well as causing cataract associated with other diseases, including myopathies. To date, more than 300 crystallin sequence variants causing cataract have been identified. Methods Here we aimed to identify the genetic basis of disease in five multi-generation British families and five sporadic cases with autosomal dominant congenital cataract using whole exome sequencing, with identified variants validated using Sanger sequencing. Following bioinformatics analysis, rare or novel variants with a moderate to damaging pathogenicity score, were filtered out and tested for segregation within the families. Results We have identified 10 different heterozygous crystallin variants. Five recurrent variants were found: family-A, with a missense variant (c.145C>T; p.R49C) in CRYAA associated with nuclear cataract; family-B, with a deletion in CRYBA1 (c.272delGAG; p.G91del) associated with nuclear cataract; and family-C, with a truncating variant in CRYGD (c.470G>A; W157*) causing a lamellar phenotype; individuals I and J had variants in CRYGC (c.13A>C; T5P) and in CRYGD (c.418C>T; R140*) causing unspecified congenital cataract and nuclear cataract, respectively. Five novel disease-causing variants were also identified: family D harboured a variant in CRYGC (c.179delG; R60Qfs*) responsible for a nuclear phenotype; family E, harboured a variant in CRYBB1 (c.656G>A; W219*) associated with lamellar cataract; individual F had a variant in CRYGD (c.392G>A; W131*) associated with nuclear cataract; and individuals G and H had variants in CRYAA (c.454delGCC; A152del) and in CRYBB1 (c.618C>A; Y206*) respectively, associated with unspecified congenital cataract. All novel variants were predicted to be pathogenic and to be moderately or highly damaging. Conclusions We report five novel variants and five known variants. Some are rare variants that have been reported previously in small ethnic groups but here we extend this to the wider population and record a broader phenotypic spectrum for these variants.
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Affiliation(s)
- Vanita Berry
- Department of Genetics, UCL Institute of Ophthalmology, University College London, 11-43 Bath Street, London, EC1V 9EL, UK. .,Moorfields Eye Hospital NHS Foundation Trust, London, EC1V 2PD, UK.
| | - Alex Ionides
- Moorfields Eye Hospital NHS Foundation Trust, London, EC1V 2PD, UK
| | - Nikolas Pontikos
- Department of Genetics, UCL Institute of Ophthalmology, University College London, 11-43 Bath Street, London, EC1V 9EL, UK.,Moorfields Eye Hospital NHS Foundation Trust, London, EC1V 2PD, UK
| | - Michalis Georgiou
- Department of Genetics, UCL Institute of Ophthalmology, University College London, 11-43 Bath Street, London, EC1V 9EL, UK.,Moorfields Eye Hospital NHS Foundation Trust, London, EC1V 2PD, UK
| | - Jing Yu
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, OX3 9DU, UK
| | - Louise A Ocaka
- GOSgene, Genetics and Genomic Medicine, UCL Great Ormond Street Institute of Child Health, London, WC1N 1EH, UK
| | - Anthony T Moore
- Moorfields Eye Hospital NHS Foundation Trust, London, EC1V 2PD, UK.,Ophthalmology Department, University of California School of Medicine, San Francisco, CA, 94158, USA
| | - Roy A Quinlan
- Department of Biosciences, University of Durham, Upper Mountjoy Science Site, Durham, DH1 3LE, UK
| | - Michel Michaelides
- Department of Genetics, UCL Institute of Ophthalmology, University College London, 11-43 Bath Street, London, EC1V 9EL, UK. .,Moorfields Eye Hospital NHS Foundation Trust, London, EC1V 2PD, UK.
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20
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He Y, Kang J, Song J. ATP differentially antagonizes the crowding-induced destabilization of human γS-crystallin and its four cataract-causing mutants. Biochem Biophys Res Commun 2020; 533:913-918. [PMID: 33004175 DOI: 10.1016/j.bbrc.2020.09.090] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 09/22/2020] [Indexed: 12/15/2022]
Abstract
αβγ-crystallins account for ∼90% of ocular proteins in lens with concentrations ≥400 mg/ml, which has to be soluble for the whole life-span and their aggregation results in cataract. So far, four cataract-causing mutants G18V, D26G, S39C and V42 M have been identified for human γS-crystallin. Mysteriously, lens maintains ATP concentrations of 3-7 mM despite being a metabolically-quiescent organ. Here by DSF and NMR, we characterized the binding of ATP to three cataract-causing mutants of human γS-crystallin as well as its effect on the solution conformations and thermal stability. The results together decode several novel findings: 1) ATP shows no detectable binding to WT and mutants, as well as no significant alternation of their conformations even at molar ratio of 1:200.2) Cataract-causing mutants show distinctive patterns of the crowding-induced destabilization. 3) ATP differentially antagonizes their crowding-induced destabilization. Our studies suggest that the crowding-induced destabilization of human γS-crystallin is also critically dependent of the hydration shell which could be differentially altered by four mutations. Most unexpectedly, ATP acts as an effective mediator for the protein hydration shell to antagonize the crowding-induced destabilization.
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Affiliation(s)
- Yuan He
- Department of Biological Sciences, Faculty of Science, National University of Singapore, 10 Kent Ridge Crescent, 119260, Singapore
| | - Jian Kang
- Department of Biological Sciences, Faculty of Science, National University of Singapore, 10 Kent Ridge Crescent, 119260, Singapore
| | - Jianxing Song
- Department of Biological Sciences, Faculty of Science, National University of Singapore, 10 Kent Ridge Crescent, 119260, Singapore.
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21
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Cataract-Associated New Mutants S175G/H181Q of βΒ2-Crystallin and P24S/S31G of γD-Crystallin Are Involved in Protein Aggregation by Structural Changes. Int J Mol Sci 2020; 21:ijms21186504. [PMID: 32899552 PMCID: PMC7555777 DOI: 10.3390/ijms21186504] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 08/21/2020] [Accepted: 09/01/2020] [Indexed: 12/15/2022] Open
Abstract
β/γ-Crystallins, the main structural protein in human lenses, have highly stable structure for keeping the lens transparent. Their mutations have been linked to cataracts. In this study, we identified 10 new mutations of β/γ-crystallins in lens proteomic dataset of cataract patients using bioinformatics tools. Of these, two double mutants, S175G/H181Q of βΒ2-crystallin and P24S/S31G of γD-crystallin, were found mutations occurred in the largest loop linking the distant β-sheets in the Greek key motif. We selected these double mutants for identifying the properties of these mutations, employing biochemical assay, the identification of protein modifications with nanoUPLC-ESI-TOF tandem MS and examining their structural dynamics with hydrogen/deuterium exchange-mass spectrometry (HDX-MS). We found that both double mutations decrease protein stability and induce the aggregation of β/γ-crystallin, possibly causing cataracts. This finding suggests that both the double mutants can serve as biomarkers of cataracts.
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22
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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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23
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He Y, Kang J, Song J. Cataract-causing G18V eliminates the antagonization by ATP against the crowding-induced destabilization of human γS-crystallin. Biochem Biophys Res Commun 2020; 530:554-560. [PMID: 32753316 DOI: 10.1016/j.bbrc.2020.07.070] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Accepted: 07/16/2020] [Indexed: 01/03/2023]
Abstract
In lens, ∼90% of ocular proteins are αβγ-crystallins with concentrations ≥400 mg/ml, which need to remain soluble for the whole life-span and their aggregation leads to cataract. The G18V mutation of human γS-crystallin causes hereditary childhood-onset cortical cataract. Mysteriously, despite being a metabolically-quiescent organ, lens maintains ATP concentrations of 3-7 mM. Very recently, we found that ATP has no significant binding to γS-crystallin as well as no alternation of its conformation. Nevertheless, ATP antagonizes the crowding-induced destabilization of γS-crystallin even at 1:1, most likely by interacting with the hydration shell. Here by DSF and NMR, we characterized the effect of ATP on binding, conformation, stability of G18V γS-crystallin and its interactions with α-crystallin. The results reveal: 1) G18V significantly accelerates the crowding-induced destabilization with Tm of 67 °C reduced to 50.5 °C at 1 mM. 2) Most unexpectedly, G18V almost completely eliminates the antagonizing effect of ATP against the crowding-induced destabilization. 3) ATP shows no significant effect on the interactions of α-crystallin with both WT and G18V γS-crystallin. Results together decode for the first time that G18V causes cataract not only by accelerating the crowding-induced destabilization, but also by eliminating the antagonizing effect of ATP against the crowding-induced destabilization.
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Affiliation(s)
- Yuan He
- Department of Biological Sciences, Faculty of Science, National University of Singapore, 10 Kent Ridge Crescent, 119260, Singapore
| | - Jian Kang
- Department of Biological Sciences, Faculty of Science, National University of Singapore, 10 Kent Ridge Crescent, 119260, Singapore
| | - Jianxing Song
- Department of Biological Sciences, Faculty of Science, National University of Singapore, 10 Kent Ridge Crescent, 119260, Singapore.
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An amyloidogenic hexapeptide from the cataract-associated γD-crystallin is a model for the full-length protein and is inhibited by naphthoquinone-tryptophan hybrids. Int J Biol Macromol 2020; 157:424-433. [DOI: 10.1016/j.ijbiomac.2020.04.079] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 04/11/2020] [Accepted: 04/11/2020] [Indexed: 12/17/2022]
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25
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Sharma V, Sharma S, Rana S, Ghosh KS. Inhibition of amyloid fibrillation of human γD-crystallin by gold nanoparticles: Studies at molecular level. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2020; 233:118199. [PMID: 32151988 DOI: 10.1016/j.saa.2020.118199] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Revised: 02/25/2020] [Accepted: 02/25/2020] [Indexed: 06/10/2023]
Abstract
The capability of citrate-stabilized gold nanoparticles (AuNps) has been explored for the inhibition of amyloid fibrillation of human γD-crystallin (HGD), a major protein of eye lens. Citrate-capped AuNps were synthesized, characterized and used further for amyloid inhibition. The results from intrinsic and extrinsic (in the presence of Thioflavin T and ANS) fluorescence based assays and CD spectroscopy clearly suggest that AuNps at nanomolar concentrations can act as an effective inhibitor against fibrillation of HGD. Fluorescence microscopic and transmission electron microscopic images also supported this observation. Considering the inhibitory role of AuNps against HGD fibrillation, interactions between HGD and AuNps were studied to decipher the mechanism of amyloid inhibition. The binding and quenching constants were calculated as ~109 M-1 using the data of tryptophan fluorescence quenching of HGD by AuNps. Ground state complexation between the protein and nanoparticles was predicted. AuNps were not found to cause any major conformational changes in the native protein. Entropy-driven complexation process between the protein and nanoparticles indicates the interactions of AuNps with hydrophobic residues of HGD. Therefore, in the presence of AuNps, the exposure of the hydrophobic patches of HGD during its partial unfolding became restricted, which results inhibition in HGD fibrillation.
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Affiliation(s)
- Vandna Sharma
- Department of Chemistry, National Institute of Technology Hamirpur, Himachal Pradesh 177005, India
| | - Shivani Sharma
- Department of Chemistry, National Institute of Technology Hamirpur, Himachal Pradesh 177005, India
| | - Shiwani Rana
- Department of Chemistry, National Institute of Technology Hamirpur, Himachal Pradesh 177005, India
| | - Kalyan Sundar Ghosh
- Department of Chemistry, National Institute of Technology Hamirpur, Himachal Pradesh 177005, India.
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Rana S, Ghosh KS. Inhibition of fibrillation of human γd-crystallin by a flavonoid morin. J Biomol Struct Dyn 2020; 39:4279-4289. [PMID: 32469293 DOI: 10.1080/07391102.2020.1775701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
To inhibit the formation of amyloid fibrils by human γd-crystallin (HGD), a series of four flavonoids (quercertin, rutin, morin and hesperetin) was tested. Only morin had demonstrated significant inhibition of HGD fibrillation. Results from fluorimetric assay techniques (using thioflavin T and ANS), FTIR, circular dichroism and microscopic imaging (fluorescence microscopy and transmission electron microscopy) confirmed HGD fibrillation inhibition by morin. HGD-morin complex formation at ground state resulted tryptophan fluorescence quenching through static mechanism, which was also confirmed by determining the excited-state life time of HGD tryptophan residues. Förster resonance energy transfer occurs from HGD to morin. Synchronous, three-dimensional fluorescence, FTIR and circular dichroism results suggest that major changes in HGD conformation did not occur on binding with morin. The interactions between HGD and morin involve hydrogen bonding and/or van der Waals forces. Docking predictions also support experimental results.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Shiwani Rana
- Department of Chemistry, National Institute of Technology Hamirpur, Hamirpur, Himachal Pradesh, India
| | - Kalyan Sundar Ghosh
- Department of Chemistry, National Institute of Technology Hamirpur, Hamirpur, Himachal Pradesh, India
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27
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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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28
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He Y, Kang J, Song J. ATP antagonizes the crowding-induced destabilization of the human eye-lens protein γS-crystallin. Biochem Biophys Res Commun 2020; 526:1112-1117. [PMID: 32307080 DOI: 10.1016/j.bbrc.2020.04.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2020] [Accepted: 04/07/2020] [Indexed: 02/06/2023]
Abstract
In lens, αβγ-crystallins accounting for ∼90% of ocular proteins with concentrations >400 mg/ml need to remain soluble for the whole life-span and their aggregation can lead to cataract. Mysteriously, despite being a metabolically-quiescent organ, lens maintains ATP concentrations of 3-7 mM. Very recently, ATP was proposed to hydrotropically prevent aggregation of crystallins but the mechanism remains unexplored. Here by NMR, DLS and DSF, we characterized the association, thermal stability and conformation of the 178-residue human γS-crystallin at concentrations from 2 to 100 mg/ml in the absence and in the presence of ATP. Results together reveal for the first time that ATP does antagonize the crowding-induced destabilization, although it has no significant binding to γS-crystallin as well as no alteration of its conformation. Therefore, ATP prevents aggregation in lens by a novel mechanism, thus rationalizing the fact that declining concentrations of ATP upon being aged is related to age-related cataractogenesis. To restore the normal concentrations of ATP in lens may represent a promising therapeutic strategy to treat aggregation-causing eye diseases.
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Affiliation(s)
- Yuan He
- Department of Biological Sciences, Faculty of Science, National University of Singapore, 10 Kent Ridge Crescent, Singapore, 119260
| | - Jian Kang
- Department of Biological Sciences, Faculty of Science, National University of Singapore, 10 Kent Ridge Crescent, Singapore, 119260
| | - Jianxing Song
- Department of Biological Sciences, Faculty of Science, National University of Singapore, 10 Kent Ridge Crescent, Singapore, 119260.
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29
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Abstract
The crystallins (α, β and γ), major constituent proteins of eye lens fiber cells play their critical role in maintaining the transparency and refractive index of the lens. Under different stress factors and with aging, β- and γ-crystallins start to unfold partially leading to their aggregation. Protein aggregation in lens basically enhances light scattering and causes the vision problem, commonly known as cataract. α-crystallin as a molecular chaperone forms complexes with its substrates (β- and γ-crystallins) to prevent such aggregation. In this chapter, the structural features of β- and γ-crystallins have been discussed. Detailed structural information linked with the high stability of γC-, γD- and γS-crystallins have been incorporated. The nature of homologous and heterologous interactions among crystallins has been deciphered, which are involved in their molecular association and complex formation.
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Affiliation(s)
- Kalyan Sundar Ghosh
- Department of Chemistry, National Institute of Technology Hamirpur, Hamirpur, 177005, Himachal Pradesh, India.
| | - Priyanka Chauhan
- Department of Chemistry, National Institute of Technology Hamirpur, Hamirpur, 177005, Himachal Pradesh, India
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30
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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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31
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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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32
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Zhang K, Zhao WJ, Yao K, Yan YB. Dissimilarity in the Contributions of the N-Terminal Domain Hydrophobic Core to the Structural Stability of Lens β/γ-Crystallins. Biochemistry 2019; 58:2499-2508. [PMID: 31037943 DOI: 10.1021/acs.biochem.8b01164] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Vertebrate lens β/γ-crystallins share a conserved tertiary structure consisting of four Greek-key motifs divided into two globular domains. Numerous inherited mutations in β/γ-crystallins have been linked to cataractogenesis. In this research, the folding mechanism underlying cataracts caused by the I21N mutation in βB2 was investigated by comparing the effect of mutagenesis on the structural features and stability of four β/γ-crystallins, βB1, βB2, γC, and γD. Our results showed that the four β/γ-crystallins differ greatly in solubility and stability against various stresses. The I21N mutation greatly impaired βB2 solubility and native structure as well as its stability against denaturation induced by guanidine hydrochloride, heat treatment, and ultraviolet irradiation. However, the deleterious effects were much weaker for mutations at the corresponding sites in βB1, γC, and γD. Molecular dynamics simulations indicated that the introduction of a nonnative hydrogen bond contributed to twisting Greek-key motif I outward, which might direct the misfolding of the I21N mutant of βB2. Meanwhile, partial hydration of the hydrophobic interior of the domain induced by the mutation destabilized βB1, γC, and γD. Our findings highlight the importance of nonnative hydrogen bond formation and hydrophobic core hydration in crystallin misfolding caused by inherited mutations.
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Affiliation(s)
- Kai Zhang
- Eye Center of the Second Affiliated Hospital, School of Medicine , Zhejiang University , Hangzhou 310009 , China
| | - Wei-Jie Zhao
- State Key Laboratory of Membrane Biology, School of Life Sciences , Tsinghua University , Beijing 100084 , China
| | - Ke Yao
- Eye Center of the Second Affiliated Hospital, School of Medicine , Zhejiang University , Hangzhou 310009 , China
| | - Yong-Bin Yan
- State Key Laboratory of Membrane Biology, School of Life Sciences , Tsinghua University , Beijing 100084 , China
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33
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Bari KJ, Sharma S, Chary KVR. Sequence specific 1H, 13C and 15N resonance assignments of the C-terminal domain of human γS-crystallin. BIOMOLECULAR NMR ASSIGNMENTS 2019; 13:43-47. [PMID: 30232732 DOI: 10.1007/s12104-018-9848-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Accepted: 09/15/2018] [Indexed: 06/08/2023]
Abstract
The high solubility and stability of crystallins present in the human eye lens maintains its transparency and refractive index with negligible protein turnover. Monomeric γ-crystallins and oligomeric β-crystallins are made up of highly homologous double Greek key domains. These domains are symmetric and possess higher stability as a result of the complex topology of individual Greek key motifs. γS-crystallin is one of the most abundant structural βγ-crystallins present in the human eye lens. In order to understand the structural stability of individual domains of human γS-crystallin in isolation vis-à-vis full length protein, we set out to structurally characterize its C-terminal domain (abbreviated hereafter as γS-CTD) by solution NMR. In this direction, we have cloned, over-expressed, isolated and purified the γS-CTD. The 2D [15N-1H] HSQC recorded with uniformly 13C/15N labeled γS-CTD showed a highly dispersed spectrum indicating the protein to adopt an ordered conformation. In this paper, we report almost complete sequence-specific 1H, 13C and 15N resonance assignments of γS-CTD using a suite of heteronuclear 3D NMR experiments.
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Affiliation(s)
- Khandekar Jishan Bari
- Center for Interdisciplinary Sciences, Tata Institute of Fundamental Research, Gopanpally, Hyderabad, 500107, India
| | - Shrikant Sharma
- Center for Interdisciplinary Sciences, Tata Institute of Fundamental Research, Gopanpally, Hyderabad, 500107, India
| | - Kandala V R Chary
- Center for Interdisciplinary Sciences, Tata Institute of Fundamental Research, Gopanpally, Hyderabad, 500107, India.
- Department of Chemical Sciences, Tata Institute of Fundamental Research, 1, Homi Bhabha Road, Colaba, Mumbai, 400005, India.
- Indian Institute of Science Education and Research, Berhampur, Odisha, 760010, India.
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34
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Thorn DC, Grosas AB, Mabbitt PD, Ray NJ, Jackson CJ, Carver JA. The Structure and Stability of the Disulfide-Linked γS-Crystallin Dimer Provide Insight into Oxidation Products Associated with Lens Cataract Formation. J Mol Biol 2018; 431:483-497. [PMID: 30552875 DOI: 10.1016/j.jmb.2018.12.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 12/05/2018] [Indexed: 11/18/2022]
Abstract
The reducing environment in the eye lens diminishes with age, leading to significant oxidative stress. Oxidation of lens crystallin proteins is the major contributor to their destabilization and deleterious aggregation that scatters visible light, obscures vision, and ultimately leads to cataract. However, the molecular basis for oxidation-induced aggregation is unknown. Using X-ray crystallography and small-angle X-ray scattering, we describe the structure of a disulfide-linked dimer of human γS-crystallin that was obtained via oxidation of C24. The γS-crystallin dimer is stable at glutathione concentrations comparable to those in aged and cataractous lenses. Moreover, dimerization of γS-crystallin significantly increases the protein's propensity to form large insoluble aggregates owing to non-cooperative domain unfolding, as is observed in crystallin variants associated with early-onset cataract. These findings provide insight into how oxidative modification of crystallins contributes to cataract and imply that early-onset and age-related forms of the disease share comparable development pathways.
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Affiliation(s)
- David C Thorn
- Research School of Chemistry, The Australian National University, Acton, ACT 2601, Australia
| | - Aidan B Grosas
- Research School of Chemistry, The Australian National University, Acton, ACT 2601, Australia
| | - Peter D Mabbitt
- Research School of Chemistry, The Australian National University, Acton, ACT 2601, Australia
| | - Nicholas J Ray
- Research School of Chemistry, The Australian National University, Acton, ACT 2601, Australia
| | - Colin J Jackson
- Research School of Chemistry, The Australian National University, Acton, ACT 2601, Australia
| | - John A Carver
- Research School of Chemistry, The Australian National University, Acton, ACT 2601, Australia.
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35
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Zhu S, Xi XB, Duan TL, Zhai Y, Li J, Yan YB, Yao K. The cataract-causing mutation G75V promotes γS-crystallin aggregation by modifying and destabilizing the native structure. Int J Biol Macromol 2018; 117:807-814. [DOI: 10.1016/j.ijbiomac.2018.05.220] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Revised: 05/25/2018] [Accepted: 05/29/2018] [Indexed: 12/31/2022]
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36
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Serebryany E, Yu S, Trauger SA, Budnik B, Shakhnovich EI. Dynamic disulfide exchange in a crystallin protein in the human eye lens promotes cataract-associated aggregation. J Biol Chem 2018; 293:17997-18009. [PMID: 30242128 DOI: 10.1074/jbc.ra118.004551] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 09/14/2018] [Indexed: 12/31/2022] Open
Abstract
Increased light scattering in the eye lens due to aggregation of the long-lived lens proteins, crystallins, is the cause of cataract disease. Several mutations in the gene encoding human γD-crystallin (HγD) cause misfolding and aggregation. Cataract-associated substitutions at Trp42 cause the protein to aggregate in vitro from a partially unfolded intermediate locked by an internal disulfide bridge, and proteomic evidence suggests a similar aggregation precursor is involved in age-onset cataract. Surprisingly, WT HγD can promote aggregation of the W42Q variant while itself remaining soluble. Here, a search for a biochemical mechanism for this interaction has revealed a previously unknown oxidoreductase activity in HγD. Using in vitro oxidation, mutational analysis, cysteine labeling, and MS, we have assigned this activity to a redox-active internal disulfide bond that is dynamically exchanged among HγD molecules. The W42Q variant acts as a disulfide sink, reducing oxidized WT and forming a distinct internal disulfide that kinetically traps the aggregation-prone intermediate. Our findings suggest a redox "hot potato" competition among WT and mutant or modified polypeptides wherein variants with the lowest kinetic stability are trapped in aggregation-prone intermediate states upon accepting disulfides from more stable variants. Such reactions may occur in other long-lived proteins that function in oxidizing environments. In these cases, aggregation may be forestalled by inhibiting disulfide flow toward mutant or damaged polypeptides.
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Affiliation(s)
- Eugene Serebryany
- From the Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138
| | - Shuhuai Yu
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, 214122 Jiangsu, China
| | | | - Bogdan Budnik
- Mass Spectrometry and Proteomics Resource Laboratory, Faculty of Arts and Sciences, Harvard University, Cambridge, Massachusetts 02138
| | - Eugene I Shakhnovich
- From the Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138.
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37
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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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38
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Camilles M, Link S, Balbach J, Saalwächter K, Krushelnitsky A. Quantitative NMR study of heat-induced aggregation of eye-lens crystallin proteins under crowding conditions. BIOCHIMICA ET BIOPHYSICA ACTA. PROTEINS AND PROTEOMICS 2018; 1866:S1570-9639(18)30119-5. [PMID: 30071343 DOI: 10.1016/j.bbapap.2018.07.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 07/20/2018] [Accepted: 07/29/2018] [Indexed: 10/28/2022]
Abstract
The eye lens contains a highly concentrated, polydisperse mixture of crystallins, and a loss in transparency during cataract formation is attributed to the aggregation of these proteins. Most biochemical and biophysical studies of crystallins have been performed in diluted samples because of various physical limitations of the respective method at physiological concentrations of up to 200-400 mg/mL. We introduce a straightforward proton NMR transverse relaxometry method to quantify simultaneously proteins in the dissolved and aggregated states at these elevated concentrations, because these states significantly differ in their transverse relaxation properties. The key feature of this method is a direct observation of the protein signal in a wide range of relaxation delays, from few microseconds up to few hundred milliseconds. We applied this method to follow heat-induced aggregation of bovine α- and γB-crystallin between 60 and 200 mg/mL. We find that at 60 °C, a temperature where both crystallins still comprise a native tertiary structure, γB-crystallin aggregated at these high protein concentrations with a time constant of about 30-40 h. α-crystallin remained soluble at 60 mg/mL but formed a transparent gel at 200 mg/mL. This quantitative NMR method can be applied to investigations of other proteins and their mixtures under various aggregation conditions.
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Affiliation(s)
- Maria Camilles
- Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06120 Halle (Saale), Germany
| | - Susanne Link
- Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06120 Halle (Saale), Germany
| | - Jochen Balbach
- Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06120 Halle (Saale), Germany
| | - Kay Saalwächter
- Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06120 Halle (Saale), Germany.
| | - Alexey Krushelnitsky
- Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06120 Halle (Saale), Germany.
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39
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Abstract
Cataract is a major cause of blindness worldwide. It is characterized by lens opacification and is accompanied by extensive posttranslational modifications (PTMs) in various proteins. PTMs play an essential role in lens opacification. Several PTMs have been described in proteins isolated from relatively old human lenses, including phosphorylation, deamidation, racemization, truncation, acetylation, and methylation. An overwhelming majority of previous cataract proteomic studies have exclusively focused on crystallin proteins, which are the most abundant proteome components of the lens. To investigate the proteome of cataract markers, this chapter focuses on the proteomic research on the functional relevance of the major PTMs in crystallins of human cataractous lenses. Elucidating the role of these modifications in cataract formation has been a challenging task because they are among the most difficult PTMs to study analytically. The proteomic status of some amides presents similar properties in normal aged and cataractous lenses, whereas some may undergo greater PTMs in cataract. Therefore, it is of great importance to review the current proteomic research on crystallins, the major protein markers in different types of cataract, to elucidate the pathogenesis of this major human-blinding condition.
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Affiliation(s)
- Keke Zhang
- Eye Institute, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China; Department of Ophthalmology, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China; Key Laboratory of Myopia, Ministry of Health PR China, Shanghai, China; Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai Medical College, Fudan University, Shanghai, China
| | - Xiangjia Zhu
- Eye Institute, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China; Department of Ophthalmology, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China; Key Laboratory of Myopia, Ministry of Health PR China, Shanghai, China; Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai Medical College, Fudan University, Shanghai, China
| | - Yi Lu
- Eye Institute, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China; Department of Ophthalmology, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China; Key Laboratory of Myopia, Ministry of Health PR China, Shanghai, China; Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai Medical College, Fudan University, Shanghai, China
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40
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Gao M, Yang F, Zhang L, Su Z, Huang Y. Exploring the sequence-structure-function relationship for the intrinsically disordered βγ-crystallin Hahellin. J Biomol Struct Dyn 2017; 36:1171-1181. [PMID: 28393629 DOI: 10.1080/07391102.2017.1316519] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
βγ-Crystallins are a superfamily of proteins containing crystallin-type Greek key motifs. Some βγ-crystallin domains have been shown to bind Ca2+. Hahellin is a newly identified intrinsically disordered βγ-crystallin domain from Hahella chejuensis. It folds into a typical βγ-crystallin structure upon Ca2+ binding and acts as a Ca2+-regulated conformational switch. Besides Hahellin, another two putative βγ-crystallins from Caulobacter crescentus and Yersinia pestis are shown to be partially disordered in their apo-form and undergo large conformational changes upon Ca2+ binding, although whether they acquire a βγ-crystallin fold is not known. The extent of conformational disorder/order of a protein is determined by its amino acid sequence. To date how this sequence-structure relationship is reflected in the βγ-crystallin superfamily has not been investigated. In this work, we comparatively studied the sequence and structure of Hahellin with those of Protein S, an ordered βγ-crystallin, via various computational biophysical techniques. We found that several factors, including presence of a C-terminal disorder prone region, high content of energetic frustrations, and low contact density, may promote the formation of the disordered state of apo-Hahellin. We also analyzed the disorder propensities for other putative disordered βγ-crystallin domains. This study provides new clues for further understanding the sequence-structure-function relationship of βγ-crystallins.
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Affiliation(s)
- Meng Gao
- a Department of Biological Engineering and Institute of Biomedical and Pharmaceutical Sciences , Hubei University of Technology , Wuhan , Hubei 430068 , China
| | - Fei Yang
- a Department of Biological Engineering and Institute of Biomedical and Pharmaceutical Sciences , Hubei University of Technology , Wuhan , Hubei 430068 , China
| | - Lei Zhang
- a Department of Biological Engineering and Institute of Biomedical and Pharmaceutical Sciences , Hubei University of Technology , Wuhan , Hubei 430068 , China
| | - Zhengding Su
- a Department of Biological Engineering and Institute of Biomedical and Pharmaceutical Sciences , Hubei University of Technology , Wuhan , Hubei 430068 , China
| | - Yongqi Huang
- a Department of Biological Engineering and Institute of Biomedical and Pharmaceutical Sciences , Hubei University of Technology , Wuhan , Hubei 430068 , China
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Zm SZ, Khoshaman K, Masoudi R, Hemmateenejad B, Yousefi R. The structural alteration and aggregation propensity of glycated lens crystallins in the presence of calcium: Importance of lens calcium homeostasis in development of diabetic cataracts. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2017; 170:174-183. [PMID: 27434877 DOI: 10.1016/j.saa.2016.07.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2016] [Revised: 06/21/2016] [Accepted: 07/08/2016] [Indexed: 06/06/2023]
Abstract
The imbalance of the calcium homeostasis in the lenticular tissues of diabetic patients is an important risk factor for development of cataract diseases. In the current study, the impact of elevated levels of calcium ions were investigated on structure and aggregation propensity of glycated lens crystallins using gel electrophoresis and spectroscopic assessments. The glycated proteins indicated significant resistance against calcium-induced structural insults and aggregation. While, glycated crystallins revealed an increased conformational stability; a slight instability was observed for these proteins upon interaction with calcium ions. Also, in the presence of calcium, the proteolytic pattern of native crystallins was altered and that of glycated protein counterparts remained almost unchanged. According to results of this study it is suggested that the structural alteration of lens crystallins upon glycation may significantly reduce their calcium buffering capacity in eye lenses. Therefore, under chronic hyperglycemia accumulation of this cataractogenic metal ion in the lenticular tissues may subsequently culminate in activation of different pathogenic pathways, leading to development of lens opacity and cataract diseases.
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Affiliation(s)
- Sara Zafaranchi Zm
- Protein Chemistry Laboratory (PCL), Department of Biology, College of Sciences, Shiraz University, Shiraz, Iran
| | - Kazem Khoshaman
- Protein Chemistry Laboratory (PCL), Department of Biology, College of Sciences, Shiraz University, Shiraz, Iran
| | - Raheleh Masoudi
- Department of Biology, College of Sciences, Shiraz University, Shiraz, Iran
| | | | - Reza Yousefi
- Protein Chemistry Laboratory (PCL), Department of Biology, College of Sciences, Shiraz University, Shiraz, Iran.
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Serebryany E, Woodard JC, Adkar BV, Shabab M, King JA, Shakhnovich EI. An Internal Disulfide Locks a Misfolded Aggregation-prone Intermediate in Cataract-linked Mutants of Human γD-Crystallin. J Biol Chem 2016; 291:19172-83. [PMID: 27417136 DOI: 10.1074/jbc.m116.735977] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Indexed: 11/06/2022] Open
Abstract
Considerable mechanistic insight has been gained into amyloid aggregation; however, a large number of non-amyloid protein aggregates are considered "amorphous," and in most cases, little is known about their mechanisms. Amorphous aggregation of γ-crystallins in the eye lens causes cataract, a widespread disease of aging. We combined simulations and experiments to study the mechanism of aggregation of two γD-crystallin mutants, W42R and W42Q: the former a congenital cataract mutation, and the latter a mimic of age-related oxidative damage. We found that formation of an internal disulfide was necessary and sufficient for aggregation under physiological conditions. Two-chain all-atom simulations predicted that one non-native disulfide in particular, between Cys(32) and Cys(41), was likely to stabilize an unfolding intermediate prone to intermolecular interactions. Mass spectrometry and mutagenesis experiments confirmed the presence of this bond in the aggregates and its necessity for oxidative aggregation under physiological conditions in vitro Mining the simulation data linked formation of this disulfide to extrusion of the N-terminal β-hairpin and rearrangement of the native β-sheet topology. Specific binding between the extruded hairpin and a distal β-sheet, in an intermolecular chain reaction similar to domain swapping, is the most probable mechanism of aggregate propagation.
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Affiliation(s)
- Eugene Serebryany
- From the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 and
| | - Jaie C Woodard
- the Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138
| | - Bharat V Adkar
- the Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138
| | - Mohammed Shabab
- From the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 and
| | - Jonathan A King
- From the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 and
| | - Eugene I Shakhnovich
- the Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138
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Structural study of the G57W mutant of human gamma-S-crystallin, associated with congenital cataract. Mol Vis 2016; 22:771-82. [PMID: 27440995 PMCID: PMC4943855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2016] [Accepted: 07/12/2016] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Human γS-crystallin (CrygS) is an important component of the human eye lens nucleus and cortex. The mutation G57W in the molecule is reported to be associated with congenital cataract in children. We compare the conformational features and aggregation properties of the mutant protein G57W with the wild-type CrygS to understand how the structural changes in the mutant are related to the mechanism of opacification. METHODS Wild-type and mutant proteins were cloned, expressed, and purified, and their structural properties were studied in solution. Conformational features and the structural stability of the proteins were compared in solution, using circular dichroism (CD) and fluorescence spectroscopic analysis, and the proteins' tendencies to aggregate were compared using extrinsic spectral probes. In addition, we analyzed the proteins' structural differences with extensive molecular modeling in silico. RESULTS CD and intrinsic fluorescence analysis suggested the secondary and tertiary structures of the mutant are slightly altered. Experiments using extrinsic spectral probes revealed that the compact close-packed structure is loosened somewhat, and the mutant tends to self-aggregate. Denaturation (both thermal and chemical) studies indicate that the replacement of glycine (G) in position 57 by tryptophan (W) lowered the structural stability of the molecule. Further, the mutant had a tendency to precipitate and scatters light more easily than the wild-type. CONCLUSIONS The replacement of glycine at position 57 by the tryptophan residue in human γS-crystallin weakens the stability of the mutant molecule and causes the molecule to self-aggregate, thus generating light-scattering particles. This set of changes in the mutant offers a molecular insight into the mechanism of opacification.
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O'Brien C, Blanco M, Costanzo J, Enterline M, Fernandez E, Robinson A, Roberts C. Modulating non-native aggregation and electrostatic protein-protein interactions with computationally designed single-point mutations. Protein Eng Des Sel 2016; 29:231-243. [PMID: 27160179 PMCID: PMC4867096 DOI: 10.1093/protein/gzw010] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Revised: 02/29/2016] [Accepted: 03/28/2016] [Indexed: 11/14/2022] Open
Abstract
Non-native protein aggregation is a ubiquitous challenge in the production, storage and administration of protein-based biotherapeutics. This study focuses on altering electrostatic protein-protein interactions as a strategy to modulate aggregation propensity in terms of temperature-dependent aggregation rates, using single-charge variants of human γ-D crystallin. Molecular models were combined to predict amino acid substitutions that would modulate protein-protein interactions with minimal effects on conformational stability. Experimental protein-protein interactions were quantified by the Kirkwood-Buff integrals (G22) from laser scattering, and G22 showed semi-quantitative agreement with model predictions. Experimental initial-rates for aggregation showed that increased (decreased) repulsive interactions led to significantly increased (decreased) aggregation resistance, even based solely on single-point mutations. However, in the case of a particular amino acid (E17), the aggregation mechanism was altered by substitution with R or K, and this greatly mitigated improvements in aggregation resistance. The results illustrate that predictions based on native protein-protein interactions can provide a useful design target for engineering aggregation resistance; however, this approach needs to be balanced with consideration of how mutations can impact aggregation mechanisms.
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Affiliation(s)
- C.J. O'Brien
- Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19716, USA
| | - M.A. Blanco
- Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19716, USA
| | - J.A. Costanzo
- Department of Chemical Engineering, University of Virginia, Charlottesville, VA 22903, USA
| | - M. Enterline
- Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19716, USA
| | - E.J. Fernandez
- Department of Chemical Engineering, University of Virginia, Charlottesville, VA 22903, USA
| | - A.S. Robinson
- Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19716, USA
- Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, LA 70118, USA
| | - C.J. Roberts
- Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19716, USA
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Khago D, Wong EK, Kingsley CN, Freites JA, Tobias DJ, Martin RW. Increased hydrophobic surface exposure in the cataract-related G18V variant of human γS-crystallin. Biochim Biophys Acta Gen Subj 2015; 1860:325-32. [PMID: 26459004 DOI: 10.1016/j.bbagen.2015.09.022] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Revised: 09/26/2015] [Accepted: 09/30/2015] [Indexed: 11/24/2022]
Abstract
BACKGROUND The objective of this study was to determine whether the cataract-related G18V variant of human γS-crystallin has increased exposure of hydrophobic residues that could explain its aggregation propensity and/or recognition by αB-crystallin. METHODS We used an ANS fluorescence assay and NMR chemical shift perturbation to experimentally probe exposed hydrophobic surfaces. These results were compared to flexible docking simulations of ANS molecules to the proteins, starting with the solution-state NMR structures of γS-WT and γS-G18V. RESULTS γS-G18V exhibits increased ANS fluorescence, suggesting increased exposed hydrophobic surface area. The specific residues involved in ANS binding were mapped by NMR chemical shift perturbation assays, revealing ANS binding sites in γS-G18V that are not present in γS-WT. Molecular docking predicts three binding sites that are specific to γS-G18V corresponding to the exposure of a hydrophobic cavity located at the interdomain interface, as well as two hydrophobic patches near a disordered loop containing solvent-exposed cysteines, all but one of which is buried in γS-WT. CONCLUSIONS Although both proteins display non-specific binding, more residues are involved in ANS binding to γS-G18V, and the affected residues are localized in the N-terminal domain and the nearby interdomain interface, proximal to the mutation site. GENERAL SIGNIFICANCE Characterization of changes in exposed hydrophobic surface area between wild-type and variant proteins can help elucidate the mechanisms of aggregation propensity and chaperone recognition, presented here in the context of cataract formation. Experimental data and simulations provide complementary views of the interactions between proteins and the small molecule probes commonly used to study aggregation. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.
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Affiliation(s)
- Domarin Khago
- Department of Chemistry, University of California, Irvine, Irvine, CA 92697, United States
| | - Eric K Wong
- Department of Chemistry, University of California, Irvine, Irvine, CA 92697, United States
| | - Carolyn N Kingsley
- Department of Chemistry, University of California, Irvine, Irvine, CA 92697, United States
| | - J Alfredo Freites
- Department of Chemistry, University of California, Irvine, Irvine, CA 92697, United States
| | - Douglas J Tobias
- Department of Chemistry, University of California, Irvine, Irvine, CA 92697, United States.
| | - Rachel W Martin
- Department of Chemistry, University of California, Irvine, Irvine, CA 92697, United States; Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697, United States.
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Vendra VPR, Khan I, Chandani S, Muniyandi A, Balasubramanian D. Gamma crystallins of the human eye lens. Biochim Biophys Acta Gen Subj 2015; 1860:333-43. [PMID: 26116913 DOI: 10.1016/j.bbagen.2015.06.007] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 06/08/2015] [Accepted: 06/19/2015] [Indexed: 01/12/2023]
Abstract
BACKGROUND Protein crystallins co me in three types (α, β and γ) and are found predominantly in the eye, and particularly in the lens, where they are packed into a compact, plastic, elastic, and transparent globule of proper refractive power range that aids in focusing incoming light on to the retina. Of these, the γ-crystallins are found largely in the nuclear region of the lens at very high concentrations (>400 mg/ml). The connection between their structure and inter-molecular interactions and lens transparency is an issue of particular interest. SCOPE OF REVIEW We review the origin and phylogeny of the gamma crystallins, their special structure involving the use of Greek key supersecondary structural motif, and how they aid in offering the appropriate refractive index gradient, intermolecular short range attractive interactions (aiding in packing them into a transparent ball), the role that several of the constituent amino acid residues play in this process, the thermodynamic and kinetic stability and how even single point mutations can upset this delicate balance and lead to intermolecular aggregation, forming light-scattering particles which compromise transparency. We cite several examples of this, and illustrate this by cloning, expressing, isolating and comparing the properties of the mutant protein S39C of human γS-crystallin (associated with congenital cataract-microcornea), with those of the wild type molecule. In addition, we note that human γ-crystallins are also present in other parts of the eye (e.g., retina), where their functions are yet to be understood. MAJOR CONCLUSIONS There are several 'crucial' residues in and around the Greek key motifs which are essential to maintain the compact architecture of the crystallin molecules. We find that a mutation that replaces even one of these residues can lead to reduction in solubility, formation of light-scattering particles and loss of transparency in the molecular assembly. GENERAL SIGNIFICANCE Such a molecular understanding of the process helps us construct the continuum of genotype-molecular structural phenotype-clinical (pathological) phenotype. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.
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Affiliation(s)
- Venkata Pulla Rao Vendra
- Ophthalmic Molecular Genetics Section, National Eye Institute, Building 5635FL, Room 1S24, 5625 Fishers Lane, Rockville, MD 20852, United States.
| | - Ismail Khan
- Prof. Brien Holden Eye Research Centre, Hyderabad Eye Research Foundation, L. V. Prasad Eye Institute, Hyderabad 500034 Telangana, India.
| | - Sushil Chandani
- Plot 32, LIC Colony, W Marredpally, Secunderabad 500026, Telangana, India.
| | - Anbukkarasi Muniyandi
- Department of Animal Science, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu, India.
| | - Dorairajan Balasubramanian
- Prof. Brien Holden Eye Research Centre, Hyderabad Eye Research Foundation, L. V. Prasad Eye Institute, Hyderabad 500034 Telangana, India.
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Garg DK, Tomar R, Dhoke RR, Srivastava A, Kundu B. Domains of Pyrococcus furiosus l-asparaginase fold sequentially and assemble through strong intersubunit associative forces. Extremophiles 2015; 19:681-91. [DOI: 10.1007/s00792-015-0748-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 03/29/2015] [Indexed: 11/29/2022]
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Serebryany E, King JA. Wild-type human γD-crystallin promotes aggregation of its oxidation-mimicking, misfolding-prone W42Q mutant. J Biol Chem 2015; 290:11491-503. [PMID: 25787081 DOI: 10.1074/jbc.m114.621581] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Indexed: 11/06/2022] Open
Abstract
Non-native protein conformers generated by mutation or chemical damage template aggregation of wild-type, undamaged polypeptides in diseases ranging from amyotrophic lateral sclerosis to cancer. We tested for such interactions in the natively monomeric human eye lens protein γd-crystallin, whose aggregation leads to cataract disease. The oxidation-mimicking W42Q mutant of γd-crystallin formed non-native polymers starting from a native-like state under physiological conditions. Aggregation occurred in the temperature range 35-45 °C, in which the mutant protein began to lose the native conformation of its N-terminal domain. Surprisingly, wild-type γd-crystallin promoted W42Q polymerization in a catalytic manner, even at mutant concentrations too low for homogeneous nucleation to occur. The presence of wild-type protein also downshifted the temperature range of W42Q aggregation. W42Q aggregation required formation of a non-native intramolecular disulfide bond but not intermolecular cross-linking. Transient WT/W42Q binding may catalyze this oxidative misfolding event in the mutant. That a more stable variant in a mixture can specifically promote aggregation of a less stable one rationalizes how extensive aggregation of rare damaged polypeptides can occur during the course of aging.
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Affiliation(s)
- Eugene Serebryany
- From the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Jonathan A King
- From the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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Kingsley CN, Bierma JC, Pham V, Martin RW. γS-crystallin proteins from the Antarctic nototheniid toothfish: a model system for investigating differential resistance to chemical and thermal denaturation. J Phys Chem B 2014; 118:13544-53. [PMID: 25372016 PMCID: PMC4254003 DOI: 10.1021/jp509134d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
![]()
The γS1- and γS2-crystallins,
structural eye lens proteins
from the Antarctic toothfish (Dissostichus mawsoni), are homologues of the human lens protein γS-crystallin.
Although γS1 has the higher thermal stability of the two, it
is more susceptible to chemical denaturation by urea. The lower thermodynamic
stability of both toothfish crystallins relative to human γS-crystallin
is consistent with the current picture of how proteins from organisms
endemic to perennially cold environments have achieved low-temperature
functionality via greater structural flexibility. In some respects,
the sequences of γS1- and γS2-crystallin are typical of
psychrophilic proteins; however, their amino acid compositions also
reflect their selection for a high refractive index increment. Like
their counterparts in the human lens and those of mesophilic fish,
both toothfish crystallins are relatively enriched in aromatic residues
and methionine and exiguous in aliphatic residues. The sometimes contradictory
requirements of selection for cold tolerance and high refractive index
make the toothfish crystallins an excellent model system for further
investigation of the biophysical properties of structural proteins.
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Affiliation(s)
- Carolyn N Kingsley
- Department of Chemistry, University of California-Irvine , 1102 Natural Sciences 2, Irvine, California, 92697-2025, United States
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Wu JW, Chen ME, Wen WS, Chen WA, Li CT, Chang CK, Lo CH, Liu HS, Wang SSS. Comparative analysis of human γD-crystallin aggregation under physiological and low pH conditions. PLoS One 2014; 9:e112309. [PMID: 25389780 PMCID: PMC4229192 DOI: 10.1371/journal.pone.0112309] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2014] [Accepted: 10/04/2014] [Indexed: 11/19/2022] Open
Abstract
Cataract, a major cause of visual impairment worldwide, is the opacification of the eye’s crystalline lens due to aggregation of the crystallin proteins. The research reported here is aimed at investigating the aggregating behavior of γ-crystallin proteins in various incubation conditions. Thioflavin T binding assay, circular dichroism spectroscopy, 1-anilinonaphthalene-8-sulfonic acid fluorescence spectroscopy, intrinsic (tryptophan) fluorescence spectroscopy, light scattering, and electron microscopy were used for structural characterization. Molecular dynamics simulations and bioinformatics prediction were performed to gain insights into the γD-crystallin mechanisms of fibrillogenesis. We first demonstrated that, except at pH 7.0 and 37°C, the aggregation of γD-crystallin was observed to be augmented upon incubation, as revealed by turbidity measurements. Next, the types of aggregates (fibrillar or non-fibrillar aggregates) formed under different incubation conditions were identified. We found that, while a variety of non-fibrillar, granular species were detected in the sample incubated under pH 7.0, the fibrillogenesis of human γD-crystallin could be induced by acidic pH (pH 2.0). In addition, circular dichroism spectroscopy, 1-anilinonaphthalene-8-sulfonic acid fluorescence spectroscopy, and intrinsic fluorescence spectroscopy were used to characterize the structural and conformational features in different incubation conditions. Our results suggested that incubation under acidic condition led to a considerable change in the secondary structure and an enhancement in solvent-exposure of the hydrophobic regions of human γD-crystallin. Finally, molecular dynamics simulations and bioinformatics prediction were performed to better explain the differences between the structures and/or conformations of the human γD-crystallin samples and to reveal potential key protein region involved in the varied aggregation behavior. Bioinformatics analyses revealed that the initiation of amyloid formation of human γD-crystallin may be associated with a region within the C-terminal domain. We believe the results from this research may contribute to a better understanding of the possible mechanisms underlying the pathogenesis of senile nuclear cataract.
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Affiliation(s)
- Josephine W. Wu
- Department of Optometry, Central Taiwan University of Science and Technology, Taichung 40601, Taiwan
- * E-mail: (JWW); (SSW)
| | - Mei-Er Chen
- Department of Entomology, National Chung Hsing University, Taichung 402, Taiwan
| | - Wen-Sing Wen
- Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan
| | - Wei-An Chen
- Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan
| | - Chien-Ting Li
- Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan
| | - Chih-Kai Chang
- Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan
| | - Chun-Hsien Lo
- Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan
| | - Hwai-Shen Liu
- Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan
| | - Steven S.-S. Wang
- Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan
- * E-mail: (JWW); (SSW)
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