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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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Zhu S, Xi Y, Xu J, Hu L, Luo C, Yao K, Chen X. The 18th amino acid glycine plays an essential role in maintaining the structural stabilities of γS-crystallin linking with congenital cataract. Int J Biol Macromol 2023; 251:126339. [PMID: 37586630 DOI: 10.1016/j.ijbiomac.2023.126339] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 08/11/2023] [Accepted: 08/12/2023] [Indexed: 08/18/2023]
Abstract
γS-crystallin is particularly rich in the embryonic nuclear region and is crucial to the maintenance of lens transparency and optical properties. Gene mutations in crystallin are the main factors leading to congenital hereditary cataracts, which are a major cause of visual impairment in children. Some mutations located in the 18th amino acid glycine of γS-crystallin were reported to be linking with congenital cataracts. However, the pathogenic mechanism has not been elucidated. Interestingly, we previously identified a novel variant of γS-crystallin (c.53G > A; p. G18D) with progressive cortical and sutural congenital cataracts in one Chinese family. In this study, we purified the γS-crystallin wildtype and mutant proteins to investigate the effects of the G18D mutation on the structural stability of γS-crystallin. The results showed that there were tertiary structural differences between the wild-type γS-crystallin and the G18D variant. The mutation significantly impaired the stability of γS-crystallin under environmental stress and promoted aggregation. Furthermore, molecular dynamics (MD) simulations showed that the mutation altered H-bonding and surface electrostatic potential. Significantly decreased stability along with an increased tendency to aggregate under environmental stress may be the major pathogenic factors for cataracts induced by the G18D mutation.
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Affiliation(s)
- Sha Zhu
- Eye Center, The Second Affiliated Hospital, School of Medicine, Zhejiang University, Zhejiang Provincial Key Laboratory of Ophthalmology, Zhejiang Provincial Clinical Research Center for Eye Diseases, Zhejiang Provincial Engineering Institute on Eye Diseases, Hangzhou 310009, Zhejiang, China
| | - Yibo Xi
- State Key Laboratory of Membrane Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Jingjie Xu
- Eye Center, The Second Affiliated Hospital, School of Medicine, Zhejiang University, Zhejiang Provincial Key Laboratory of Ophthalmology, Zhejiang Provincial Clinical Research Center for Eye Diseases, Zhejiang Provincial Engineering Institute on Eye Diseases, Hangzhou 310009, Zhejiang, China
| | - Lidan Hu
- State Key Laboratory of Membrane Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China; The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou 310052, China
| | - Chenqi Luo
- Eye Center, The Second Affiliated Hospital, School of Medicine, Zhejiang University, Zhejiang Provincial Key Laboratory of Ophthalmology, Zhejiang Provincial Clinical Research Center for Eye Diseases, Zhejiang Provincial Engineering Institute on Eye Diseases, Hangzhou 310009, Zhejiang, China
| | - Ke Yao
- Eye Center, The Second Affiliated Hospital, School of Medicine, Zhejiang University, Zhejiang Provincial Key Laboratory of Ophthalmology, Zhejiang Provincial Clinical Research Center for Eye Diseases, Zhejiang Provincial Engineering Institute on Eye Diseases, Hangzhou 310009, Zhejiang, China.
| | - Xiangjun Chen
- Eye Center, The Second Affiliated Hospital, School of Medicine, Zhejiang University, Zhejiang Provincial Key Laboratory of Ophthalmology, Zhejiang Provincial Clinical Research Center for Eye Diseases, Zhejiang Provincial Engineering Institute on Eye Diseases, Hangzhou 310009, Zhejiang, China; Institute of Translational Medicine, Zhejiang University School of Medicine, 268 Kaixuan Road, Hangzhou 310020, China.
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3
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Srivastava O, Wilson L, Barnes S, Srivastava K, Joseph R. αA and αB peptides from human cataractous lenses show antichaperone activity and enhance aggregation of lens proteins. Mol Vis 2022; 28:147-164. [PMID: 36540064 PMCID: PMC9744240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Accepted: 08/04/2022] [Indexed: 12/30/2022] Open
Abstract
Purpose To identify and characterize properties of αA- and αB-crystallins' low molecular weight peptides (molecular weight [Mr] < 5 kDa) that were present in a 62-year-old human nuclear cataract, but not in normal 62-year-old human lenses. Methods Low molecular weight peptides (< 5 kDa) were isolated with a trichloroacetic acid (TCA) solubilization method from water-soluble (WS) and water-insoluble (WI) proteins of nuclear cataractous lenses of a 62-year-old donor and normal human lenses from an age-matched donor. Five commercially synthesized peptides (found only in cataractous lenses and not in normal lenses) were used to determine their chaperone and antichaperone activity and aggregation properties. Results Mass spectrometric analysis showed 28 peptides of αA-crystallin and 38 peptides of αB-crystallin were present in the cataractous lenses but not in the normal lenses. Two αA peptides (named αAP1 and αAP2; both derived from the αA N-terminal domain (NTD) region) and three αB peptides (named αBP3, αBP4, and αBP5, derived from the αB NTD-, core domain (CD), and C-terminal extension (CTE) regions, respectively) were commercially synthesized. αAP1 inhibited the chaperone activity of αA- and αB-crystallins, but the other four peptides (αAP2, αBP3, αBP4, and αBP5) exhibited mixed effects on chaperone activity. Upon incubation with human WS proteins and peptides in vitro, the αBP4 peptide showed higher aggregation properties relative to the αAP1 peptide. During in vivo experiments, the cell-penetrating polyarginine-labeled αAP1 and αBP4 peptides showed 57% and 85% aggregates, respectively, around the nuclei of cultured human lens epithelial cells compared to only 35% by a scrambled peptide. Conclusions The antichaperone activity of the αAP1 peptide and the aggregation property of the αBP4 peptide with lens proteins could play a potential role during the development of lens opacity.
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Affiliation(s)
- Om Srivastava
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, AL
| | - Landon Wilson
- Targeted Metabolomics and Proteomics Laboratory, University of Alabama at Birmingham, Birmingham, AL
| | - Stephen Barnes
- Department of Pharmacology and Toxicology, University of Alabama at Birmingham, Birmingham, AL,Targeted Metabolomics and Proteomics Laboratory, University of Alabama at Birmingham, Birmingham, AL
| | - Kiran Srivastava
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, AL
| | - Roy Joseph
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, AL
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Xu W, Xu J, Shi C, Wu J, Wang H, Wu W, Chen X, Hu L. A novel cataract-causing mutation Ile82Met of γA crystallin trends to aggregate with unfolding intermediate. Int J Biol Macromol 2022; 211:357-367. [PMID: 35513103 DOI: 10.1016/j.ijbiomac.2022.04.205] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2021] [Revised: 02/06/2022] [Accepted: 04/27/2022] [Indexed: 11/05/2022]
Abstract
Cataract is the most common pathogenic ophthalmic disease leading to blindness in children worldwide. Genetic disorder is the leading cause of congenital cataract, among which crystallin mutations have a high incidence. There are few reports on γA-crystallin, one critical member of crystallin superfamilies. In this study, we identified a novel pathogenic mutation (Ile82Met) in γA-crystallin from a three-generation Chinese family with cataract, and investigated the potential molecular mechanism in detail. To elucidate the pathogenic mechanism of I82M mutant, spectroscopic and solubility experiments were performed to determine the difference between the purified γA-crystallin wild type (WT) and I82M mutant under both physiological conditions and environmental stresses (UV irradiation, thermal denaturation or chemical denaturation). The I82M mutant did not affect the secondary/tertiary structure of monomeric γA-crystallin under physiological status, but decreased protein stability and increased aggregatory potency under the stressful treatment. Surprisingly, the chemical denaturation caused I82M to switch from the two-state unfolding of γA-crystallin to three-state unfolding involving an unfolding intermediate. This study expands the genetic variation map of cataract, and provides novel insights into the pathomechanism, in particular, filling in a gap in the understanding of γA-crystallin mutants causing cataract.
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Affiliation(s)
- Wanyue Xu
- The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou 310052, China; Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China; Institute of Translational Medicine, Zhejiang University School of Medicine, 268 Kaixuan Road, Hangzhou 310020, China
| | - Jingjie Xu
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China
| | - Caiping Shi
- The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou 310052, China
| | - Jing Wu
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China
| | - Huaxia Wang
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China; Institute of Translational Medicine, Zhejiang University School of Medicine, 268 Kaixuan Road, Hangzhou 310020, China
| | - Wei Wu
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China
| | - Xiangjun Chen
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China; Institute of Translational Medicine, Zhejiang University School of Medicine, 268 Kaixuan Road, Hangzhou 310020, China.
| | - Lidan Hu
- The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou 310052, China.
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Wu J, Xu W, Wu W, Xu J, Zheng S, Shentu X, Chen X. Cataract-causing mutation R48C increases γA-crystallin susceptibility to oxidative stress and ultraviolet radiation. Int J Biol Macromol 2022; 194:688-694. [PMID: 34826455 DOI: 10.1016/j.ijbiomac.2021.11.113] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Revised: 11/16/2021] [Accepted: 11/16/2021] [Indexed: 01/16/2023]
Abstract
Among all congenital cataracts caused by genetic mutations, approximately half are caused by a mutation in crystallin genes, and accounts the leading cause of blindness in children globally. In this study, we investigated the underlying molecular mechanism of R48C mutation (c.142C > T; p.[Arg48Cys]) of γA-crystallin in a Mexican-Mestizo descent family causing congenital cataracts. We purified γA-crystallin wild-type (WT) and R48C mutant and compared their structural characteristics and biophysical properties by Spectroscopic experiments and environmental stress (oxidative stress, ultraviolet irradiation, pH disorders, thermal shock, or chemical denaturation). The R48C mutant did not affect the secondary and tertiary structure of monomer γA-crystallin, nor did it affect its stability to heat shock and chemicals. However, the R48C mutant destroys the oxidative stability of γA-crystallin, which makes the protein more prone to aggregation and precipitation under oxidative conditions. These might be the pathogenesis of γA-crystallin R48C mutant related to congenital cataract and help to develop anti-cataract strategies from the perspective of γA-crystallin.
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Affiliation(s)
- Jing Wu
- Department of Ophthalmology, The Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou, Zhejiang, China; Zhejiang Provincial Key Lab of Ophthalmology, 88 Jiefang Road, Hangzhou, Zhejiang, China; Department of Ophthalmology, Zhejiang Provincial People's Hospital, People's Hospital of Hangzhou Medical College, 158 Shangtang Road, Hangzhou, Zhejiang, China
| | - Wanyue Xu
- Institute of Translational Medicine, Zhejiang University School of Medicine, 268 Kaixuan Road, Hangzhou, Zhejiang, China
| | - Wei Wu
- Department of Ophthalmology, The Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou, Zhejiang, China; Zhejiang Provincial Key Lab of Ophthalmology, 88 Jiefang Road, Hangzhou, Zhejiang, China
| | - Jingjie Xu
- Department of Ophthalmology, The Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou, Zhejiang, China; Zhejiang Provincial Key Lab of Ophthalmology, 88 Jiefang Road, Hangzhou, Zhejiang, China
| | - Sifan Zheng
- GKT School of Medical Education, King's College London, London SE1 1UL, United Kingdom
| | - Xingchao Shentu
- Department of Ophthalmology, The Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou, Zhejiang, China; Zhejiang Provincial Key Lab of Ophthalmology, 88 Jiefang Road, Hangzhou, Zhejiang, China.
| | - Xiangjun Chen
- Department of Ophthalmology, The Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou, Zhejiang, China; Zhejiang Provincial Key Lab of Ophthalmology, 88 Jiefang Road, Hangzhou, Zhejiang, China; Institute of Translational Medicine, Zhejiang University School of Medicine, 268 Kaixuan Road, Hangzhou, Zhejiang, China.
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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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7
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Translation Efficiency and Degradation of ER-Associated mRNAs Modulated by ER-Anchored poly(A)-Specific Ribonuclease (PARN). Cells 2020; 9:cells9010162. [PMID: 31936572 PMCID: PMC7017053 DOI: 10.3390/cells9010162] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 01/05/2020] [Accepted: 01/07/2020] [Indexed: 12/21/2022] Open
Abstract
Translation is spatiotemporally regulated and endoplasmic reticulum (ER)-associated mRNAs are generally in efficient translation. It is unclear whether the ER-associated mRNAs are deadenylated or degraded on the ER surface in situ or in the cytosol. Here, we showed that ER possessed active deadenylases, particularly the poly(A)-specific ribonuclease (PARN), in common cell lines and mouse tissues. Consistently, purified recombinant PARN exhibited a strong ability to insert into the Langmuir monolayer and liposome. ER-anchored PARN was found to be able to reshape the poly(A) length profile of the ER-associated RNAs by suppressing long poly(A) tails without significantly influencing the cytosolic RNAs. The shortening of long poly(A) tails did not affect global translation efficiency, which suggests that the non-specific action of PARN towards long poly(A) tails was beyond the scope of translation regulation on the ER surface. Transcriptome sequencing analysis indicated that the ER-anchored PARN trigged the degradation of a small subset of ER-enriched transcripts. The ER-anchored PARN modulated the translation of its targets by redistributing ribosomes to heavy polysomes, which suggests that PARN might play a role in dynamic ribosome reallocation. During DNA damage response, MK2 phosphorylated PARN-Ser557 to modulate PARN translocation from the ER to cytosol. The ER-anchored PARN modulated DNA damage response and thereby cell viability by promoting the decay of ER-associated MDM2 transcripts with low ribosome occupancy. These findings revealed that highly regulated communication between mRNA degradation rate and translation efficiency is present on the ER surface in situ and PARN might contribute to this communication by modulating the dynamic ribosome reallocation between transcripts with low and high ribosome occupancies.
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Aguayo-Ortiz R, González-Navejas A, Palomino-Vizcaino G, Rodriguez-Meza O, Costas M, Quintanar L, Dominguez L. Thermodynamic Stability of Human γD-Crystallin Mutants Using Alchemical Free-Energy Calculations. J Phys Chem B 2019; 123:5671-5677. [PMID: 31199646 DOI: 10.1021/acs.jpcb.9b01818] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
γD-Crystallin (HγDC) is a key structural protein in the human lens, whose aggregation has been associated with the development of cataracts. Single-point mutations and post-translational modifications destabilize HγDC interactions, forming partially folded intermediates, where hydrophobic residues are exposed and thus triggering its aggregation. In this work, we used alchemical free-energy calculations to predict changes in thermodynamic stability (ΔΔG) of 10 alanine-scanning variants and 12 HγDC mutations associated with the development of congenital cataract. Our results show that W42R is the most destabilizing mutation in HγDC. This has been corroborated through experimental determination of ΔΔG employing differential scanning calorimetry. Calculations of hydration free energies from the HγDC WT and the W42R mutant suggested that the mutant has a higher aggregation propensity. Our combined theoretical and experimental results contribute to understand HγDC destabilization and aggregation mechanisms in age-onset cataracts.
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Affiliation(s)
| | | | - Giovanni Palomino-Vizcaino
- Departamento de Química , Centro de Investigación y de Estudios Avanzados (Cinvestav) , Mexico City 07360 , Mexico
| | | | | | - Liliana Quintanar
- Departamento de Química , Centro de Investigación y de Estudios Avanzados (Cinvestav) , Mexico City 07360 , Mexico
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9
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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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10
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Zhao WJ, Yan YB. Increasing susceptibility to oxidative stress by cataract-causing crystallin mutations. Int J Biol Macromol 2018; 108:665-673. [DOI: 10.1016/j.ijbiomac.2017.12.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2017] [Revised: 12/01/2017] [Accepted: 12/04/2017] [Indexed: 11/24/2022]
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11
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Whitley MJ, Xi Z, Bartko JC, Jensen MR, Blackledge M, Gronenborn AM. A Combined NMR and SAXS Analysis of the Partially Folded Cataract-Associated V75D γD-Crystallin. Biophys J 2017; 112:1135-1146. [PMID: 28355541 DOI: 10.1016/j.bpj.2017.02.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Revised: 02/03/2017] [Accepted: 02/08/2017] [Indexed: 11/19/2022] Open
Abstract
A cataract is a pathological condition characterized by the clouding of the normally clear eye lens brought about by deposition of crystallin proteins in the lens fiber cells. These protein aggregates reduce visual acuity by scattering or blocking incoming light. Chemical damage to proteins of the crystallin family, accumulated over a lifetime, leads to age-related cataract, whereas inherited mutations are associated with congenital or early-onset cataract. The V75D mutant of γD-crystallin is associated with congenital cataract in mice and was previously shown to un/fold via a partially folded intermediate. Here, we structurally characterized the stable equilibrium urea unfolding intermediate of V75D at the ensemble level using solution NMR and small-angle x-ray scattering. Our data show that, in the intermediate, the C-terminal domain retains a folded conformation that is similar to the native wild-type protein, whereas the N-terminal domain is unfolded and comprises an ensemble of random conformers, without any detectable residual structural propensities.
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Affiliation(s)
- Matthew J Whitley
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Zhaoyong Xi
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Jonathan C Bartko
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | | | - Martin Blackledge
- Institut de Biologie Structurale, CEA, CNRS, Université Grenoble Alpes, Grenoble, France
| | - Angela M Gronenborn
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
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12
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Roskamp KW, Montelongo DM, Anorma CD, Bandak DN, Chua JA, Malecha KT, Martin RW. Multiple Aggregation Pathways in Human γS-Crystallin and Its Aggregation-Prone G18V Variant. Invest Ophthalmol Vis Sci 2017; 58:2397-2405. [PMID: 28444328 PMCID: PMC5407245 DOI: 10.1167/iovs.16-20621] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Purpose Cataract results from the formation of light-scattering precipitates due to point mutations or accumulated damage in the structural crystallins of the eye lens. Although excised cataracts are predominantly amorphous, in vitro studies show that crystallins are capable of adopting a variety of morphologies depending on the preparation method. Here we characterize thermal, pH-dependent, and UV-irradiated aggregates from wild-type human γS-crystallin (γS-WT) and its aggregation-prone variant, γS-G18V. Methods Aggregates of γS-WT and γS-G18V were prepared under acidic, neutral, and basic pH conditions and held at 25°C or 37°C for 48 hours. UV-induced aggregates were produced by irradiation with a 355-nm laser. Aggregation and fibril formation were monitored via turbidity and thioflavin T (ThT) assays. Aggregates were characterized using intrinsic aromatic fluorescence, powder x-ray diffraction, and mass spectrometry. Results γS-crystallin aggregates displayed different characteristics depending on the preparation method. γS-G18V produced a larger amount of detectable aggregates than did γS-WT and at less-extreme conditions. Aggregates formed under basic and acidic conditions yielded elevated ThT fluorescence; however, aggregates formed at low pH did not produce strongly turbid solutions. UV-induced aggregates produced highly turbid solutions but displayed only moderate ThT fluorescence. X-ray diffraction confirms amyloid character in low-pH samples and UV-irradiated samples, although the relative amounts vary. Conclusions γS-G18V demonstrates increased aggregation propensity compared to γS-WT when treated with heat, acid, or UV light. The resulting aggregates differ in their ThT fluorescence and turbidity, suggesting that at least two different aggregation pathways are accessible to both proteins under the conditions tested.
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Affiliation(s)
- Kyle W Roskamp
- Department of Chemistry, University of California, Irvine, Irvine, California, United States
| | - David M Montelongo
- Department of Chemistry, University of California, Irvine, Irvine, California, United States
| | - Chelsea D Anorma
- Department of Chemistry, University of California, Irvine, Irvine, California, United States
| | - Diana N Bandak
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, California, United States
| | - Janine A Chua
- Department of Chemistry, University of California, Irvine, Irvine, California, United States
| | - Kurtis T Malecha
- Department of Chemistry, University of California, Irvine, Irvine, California, United States
| | - Rachel W Martin
- Department of Chemistry, University of California, Irvine, Irvine, California, United States 2Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, California, United States
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13
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Khan MS, Bhat SA, Tabrez S, Alama MN, Alsenaidy MA, Al-Senaidy AM. Denaturation induced aggregation in α-crystallin: differential action of chaotropes. J Mol Recognit 2016; 29:536-543. [DOI: 10.1002/jmr.2553] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Revised: 04/21/2016] [Accepted: 05/04/2016] [Indexed: 11/05/2022]
Affiliation(s)
- Mohd Shahnawaz Khan
- Protein Research Chair, Department of Biochemistry, College of Science; King Saud University; Riyadh Saudi Arabia
| | - Sheraz Ahmad Bhat
- Department of Biochemistry, Faculty of Life Sciences; Aligarh Muslim University; Aligarh India
| | - Shams Tabrez
- King Fahd Medical Research Center; King Abdulaziz University; Jeddah 21589 Saudi Arabia
| | - Mohammed Nabil Alama
- Cardiology Unit, Department of Medicine; King Abdulaziz University Hospital; Jeddah 21589 Saudi Arabia
| | - Mohammad A. Alsenaidy
- Department of Pharmaceutics, College of Pharmacy; King Saud University; Riyadh Saudi Arabia
| | - Abdulrahman M. Al-Senaidy
- Protein Research Chair, Department of Biochemistry, College of Science; King Saud University; Riyadh Saudi Arabia
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14
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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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15
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DiMauro MA, Nandi SK, Raghavan CT, Kar RK, Wang B, Bhunia A, Nagaraj RH, Biswas A. Acetylation of Gly1 and Lys2 promotes aggregation of human γD-crystallin. Biochemistry 2014; 53:7269-82. [PMID: 25393041 PMCID: PMC4245984 DOI: 10.1021/bi501004y] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
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The human lens contains three major
protein families: α-,
β-, and γ-crystallin. Among the several variants of γ-crystallin
in the human lens, γD-crystallin is a major form. γD-Crystallin
is primarily present in the nuclear region of the lens and contains
a single lysine residue at the second position (K2). In this study,
we investigated the acetylation of K2 in γD-crystallin in aging
and cataractous human lenses. Our results indicated that K2 is acetylated
at an early age and that the amount of K2-acetylated γD-crystallin
increased with age. Mass spectrometric analysis revealed that in addition
to K2, glycine 1 (G1) was acetylated in γD-crystallin from human
lenses and in γD-crystallin acetylated in vitro. The chaperone ability of α-crystallin for acetylated γD-crystallin
was lower than that for the nonacetylated protein. The tertiary structure
and the microenvironment of the cysteine residues were significantly
altered by acetylation. The acetylated protein exhibited higher surface
hydrophobicity, was unstable against thermal and chemical denaturation,
and exhibited a higher propensity to aggregate at 80 °C in comparison
to the nonacetylated protein. Acetylation enhanced the GdnHCl-induced
unfolding and slowed the subsequent refolding of γD-crystallin.
Theoretical analysis indicated that the acetylation of K2 and G1 reduced
the structural stability of the protein and brought the distal cysteine
residues (C18 and C78) into close proximity. Collectively, these results
indicate that the acetylation of G1 and K2 residues in γD-crystallin
likely induced a molten globule-like structure, predisposing it to
aggregation, which may account for the high content of aggregated
proteins in the nucleus of aged and cataractous human lenses.
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Affiliation(s)
- Michael A DiMauro
- Department of Ophthalmology and Visual Sciences and ‡Center for Proteomics and Bioinformatics, Case Western Reserve University School of Medicine , Cleveland, Ohio, United States
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16
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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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17
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Xi YB, Zhang K, Dai AB, Ji SR, Yao K, Yan YB. Cataract-linked mutation R188H promotes βB2-crystallin aggregation and fibrillization during acid denaturation. Biochem Biophys Res Commun 2014; 447:244-9. [DOI: 10.1016/j.bbrc.2014.03.119] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Accepted: 03/24/2014] [Indexed: 01/26/2023]
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18
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Leng XY, Wang S, Cao NQ, Qi LB, Yan YB. The N-terminal extension of βB1-crystallin chaperones β-crystallin folding and cooperates with αA-crystallin. Biochemistry 2014; 53:2464-73. [PMID: 24669963 DOI: 10.1021/bi500146d] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
β/γ-Crystallins are the major structural proteins in mammalian lens. The N-terminal truncation of βB1-crystallin has been associated with the regulation of β-crystallin size distributions in human lens. Herein we studied the roles of βB1 N-terminal extension in protein structure and folding by constructing five N-terminal truncated forms. The truncations did not affect the secondary and tertiary structures of the main body as well as stability against denaturation. Truncations with more than 28 residues off the N-terminus promoted the dissociation of the dimeric βB1 into monomers in diluted solutions. Interestingly, the N-terminal extension facilitated βB1 to adopt the correct folding pathway, while truncated proteins were prone to undergo the misfolding/aggregation pathway during kinetic refolding. The N-terminal extension of βB1 acted as an intramolecular chaperone (IMC) to regulate the kinetic partitioning between folding and misfolding. The IMC function of the N-terminal extension was also critical to the correct refolding of β-crystallin heteromer and the action of the lens-specific molecular chaperone αA-crystallin. The cooperation between IMC and molecular chaperones produced a much stronger chaperoning effect than if they acted separately. To our knowledge, this is the first report showing the cooperation between IMC and molecular chaperones.
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Affiliation(s)
- Xiao-Yao Leng
- State Key Laboratory of Biomembrane and Membrane Biotechnology, School of Life Sciences, Tsinghua University , Beijing 100084, China
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19
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Moran SD, Zhang TO, Zanni MT. An alternative structural isoform in amyloid-like aggregates formed from thermally denatured human γD-crystallin. Protein Sci 2014; 23:321-31. [PMID: 24415662 DOI: 10.1002/pro.2422] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Revised: 01/06/2014] [Accepted: 01/08/2014] [Indexed: 11/11/2022]
Abstract
The eye lens protein γD-crystallin contributes to cataract formation in the lens. In vitro experiments show that γD-crystallin has a high propensity to form amyloid fibers when denatured, and that denaturation by acid or UV-B photodamage results in its C-terminal domain forming the β-sheet core of amyloid fibers. Here, we show that thermal denaturation results in sheet-like aggregates that contain cross-linked oligomers of the protein, according to transmission electron microscopy and SDS-PAGE. We use two-dimensional infrared spectroscopy to show that these aggregates have an amyloid-like secondary structure with extended β-sheets, and use isotope dilution experiments to show that each protein contributes approximately one β-strand to each β-sheet in the aggregates. Using segmental (13) C labeling, we show that the organization of the protein's two domains in thermally induced aggregates results in a previously unobserved structure in which both the N-terminal and C-terminal domains contribute to β-sheets. We propose a model for the structural organization of the aggregates and attribute the recruitment of the N-terminal domain into the fiber structure to intermolecular cross linking.
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Affiliation(s)
- Sean D Moran
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706
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20
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The importance of the last strand at the C-terminus in βB2-crystallin stability and assembly. Biochim Biophys Acta Mol Basis Dis 2014; 1842:44-55. [DOI: 10.1016/j.bbadis.2013.10.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Revised: 09/29/2013] [Accepted: 10/01/2013] [Indexed: 01/15/2023]
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21
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Lam AR, Moran SD, Preketes NK, Zhang TO, Zanni MT, Mukamel S. Study of the γD-crystallin protein using two-dimensional infrared (2DIR) spectroscopy: experiment and simulation. J Phys Chem B 2013; 117:15436-43. [PMID: 23972032 DOI: 10.1021/jp405159v] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Cataracts is a misfolding protein disease in which one of the major components is the γD-crystallin protein. The conformational structure of the aggregated γD-crystallin and the interactions that cause aggregation are largely unknown. A recent experimental two-dimensional infrared (2DIR) spectroscopy study determined that the C-terminal domain has a high propensity to form β-sheets whereas the N-terminal domain forms a disordered structure in the fiber state. We present a combined computational molecular dynamics and infrared spectroscopy study of the local dynamics of these domains. The computed 2DIR signals agree remarkably well with experiment. We show that the two domains, both of which have a Greek key structural fold, experience different electrostatic environments, which may be related to the fact that the C-terminal domain is more structurally stable than the N-terminal domain. We correlate the vibrational couplings to known energy dissipation mechanisms and reveal their origin.
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Affiliation(s)
- A R Lam
- Department of Chemistry, University of California, Irvine , Irvine, California 92697-2025, United States
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22
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Wang S, Zhao WJ, Liu H, Gong H, Yan YB. Increasing βB1-crystallin sensitivity to proteolysis caused by the congenital cataract-microcornea syndrome mutation S129R. Biochim Biophys Acta Mol Basis Dis 2013; 1832:302-11. [DOI: 10.1016/j.bbadis.2012.11.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Revised: 11/07/2012] [Accepted: 11/09/2012] [Indexed: 12/22/2022]
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23
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Xu J, Wang S, Zhao WJ, Xi YB, Yan YB, Yao K. The congenital cataract-linked A2V mutation impairs tetramer formation and promotes aggregation of βB2-crystallin. PLoS One 2012; 7:e51200. [PMID: 23236454 PMCID: PMC3516508 DOI: 10.1371/journal.pone.0051200] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Accepted: 10/30/2012] [Indexed: 11/28/2022] Open
Abstract
β/γ-Crystallins, the major structural proteins in human lens, are highly conserved in their tertiary structures but distinct in the quaternary structures. The N- and C-terminal extensions have been proposed to play a crucial role in mediating the size of β-crystallin assembly. In this research, we investigated the molecular mechanism underlying the congenital hereditary cataract caused by the recently characterized A2V mutation in βB2-crystallin. Spectroscopic experiments indicated that the mutation did not affect the secondary and tertiary structures of βB2-crystallin. The mutation did not affect the formation of βB2/βA3-crystallin heteromer as well as the stability and folding of the heteromer, suggesting that the mutation might not interfere with the protein interacting network in the lens. However, the tetramerization of βB2-crystallin at high protein concentrations was retarded by the A2V mutation. The mutation slightly decreased the thermal stability and promoted the thermal aggregation of βB2-crystallin. Although it did not influence the stability of βB2-crystallin against denaturation induced by chemical denaturants and UV irradiation, the A2V mutant was more prone to be trapped in the off-pathway aggregation process during kinetic refolding. Our results suggested that the A2V mutation might lead to injury of lens optical properties by decreasing βB2-crystallin stability against heat treatment and by impairing βB2-crystallin assembly into high-order homo-oligomers.
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Affiliation(s)
- Jia Xu
- Eye Center of the 2nd Affiliated Hospital, Medical College of Zhejiang University, Hangzhou, China
| | - Sha Wang
- State Key Laboratory of Biomembrane and Membrane Biotechnology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Wei-Jie Zhao
- State Key Laboratory of Biomembrane and Membrane Biotechnology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Yi-Bo Xi
- State Key Laboratory of Biomembrane and Membrane Biotechnology, School of Life Sciences, Tsinghua University, Beijing, China
- Institute of Biophysics, Lanzhou University, Lanzhou, China
| | - Yong-Bin Yan
- State Key Laboratory of Biomembrane and Membrane Biotechnology, School of Life Sciences, Tsinghua University, Beijing, China
- * E-mail: (Y-BY); (KY)
| | - Ke Yao
- Eye Center of the 2nd Affiliated Hospital, Medical College of Zhejiang University, Hangzhou, China
- * E-mail: (Y-BY); (KY)
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24
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Cataract-causing defect of a mutant γ-crystallin proceeds through an aggregation pathway which bypasses recognition by the α-crystallin chaperone. PLoS One 2012; 7:e37256. [PMID: 22655036 PMCID: PMC3360035 DOI: 10.1371/journal.pone.0037256] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2012] [Accepted: 04/18/2012] [Indexed: 11/19/2022] Open
Abstract
Background The transparency of the eye lens depends upon maintenance of the native state of the γ- and β-crystallins, which is aided by the abundant chaperones αA- and αB-crystallin. Mature onset cataract, the leading cause of blindness worldwide, involves the polymerization of covalently damaged or partially unfolded crystallins into light-scattering aggregates. A number of single amino acid substitutions and truncations of γ-crystallins result in congenital cataract in both humans and mice, though in many cases the coupling between the protein alterations and the accumulation of aggregates is poorly defined. Methodology/Principal Findings We have studied the aggregation properties and chaperone interactions of human γD-crystallin carrying substitutions of two buried core mutants, I90F and V75D, which cause congenital cataract in mice. The in vitro aggregation pathway competing with productive refolding was not altered by either substitution. Furthermore, this aggregation pathway for both mutant proteins–originating from a partially folded intermediate–was efficiently suppressed by αB-crystallin. Thus the cataract pathology was unlikely to be associated with a direct folding defect. The native state of wild-type human γD-crystallin exhibited no tendency to aggregate under physiological conditions. However both I90F and V75D native-like proteins exhibited slow (days) aggregation to high molecular weight aggregates under physiological conditions. The perturbed conformation of I90F was recognized and bound by both αA and αB chaperones. In contrast, the aggregation derived from the perturbed state of V75D was not suppressed by either chaperone, and the aggregating species were not bound by the chaperone. Conclusions/Significance The cataract phenotype of I90F in mice may be due to premature saturation of the finite α- crystallin pool. The V75D aggregation pathway and its escape from chaperone surveillance and aggregation suppression can account for the congenital cataract pathology of this mutant. Failure of chaperone recognition may be an important source of pathology for many other protein folding defects.
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25
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Li XQ, Cai HC, Zhou SY, Yang JH, Xi YB, Gao XB, Zhao WJ, Li P, Zhao GY, Tong Y, Bao FC, Ma Y, Wang S, Yan YB, Lu CL, Ma X. A novel mutation impairing the tertiary structure and stability of γC-crystallin (CRYGC) leads to cataract formation in humans and zebrafish lens. Hum Mutat 2011; 33:391-401. [DOI: 10.1002/humu.21648] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2011] [Accepted: 10/17/2011] [Indexed: 11/09/2022]
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26
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Wang S, Leng XY, Yan YB. The Benefits of Being β-Crystallin Heteromers: βB1-Crystallin Protects βA3-Crystallin against Aggregation during Co-refolding. Biochemistry 2011; 50:10451-61. [DOI: 10.1021/bi201375p] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Sha Wang
- State Key
Laboratory of Biomembrane and Membrane Biotechnology, School of Life
Sciences, Tsinghua University, Beijing
100084, China
| | - Xiao-Yao Leng
- State Key
Laboratory of Biomembrane and Membrane Biotechnology, School of Life
Sciences, Tsinghua University, Beijing
100084, China
| | - Yong-Bin Yan
- State Key
Laboratory of Biomembrane and Membrane Biotechnology, School of Life
Sciences, Tsinghua University, Beijing
100084, China
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