1
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Chen S, Guo J, Xu W, Song H, Xu J, Luo C, Yao K, Hu L, Chen X, Yu Y. Cataract-related variant R114C increases βA3-crystallin susceptibility to environmental stresses by disrupting the protein senior structure. Int J Biol Macromol 2024; 262:130191. [PMID: 38360245 DOI: 10.1016/j.ijbiomac.2024.130191] [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: 12/31/2023] [Revised: 02/12/2024] [Accepted: 02/12/2024] [Indexed: 02/17/2024]
Abstract
Congenital cataract is a major cause of childhood blindness worldwide, with crystallin mutations accounting for over 40 % of gene-mutation-related cases. Our research focused on a novel R114C mutation in a Chinese family, resulting in bilateral coronary cataract with blue punctate opacity. Spectroscopic experiments revealed that βA3-R114C significantly altered the senior structure, exhibiting aggregation, and reduced solubility at physiological temperature. The mutant also displayed decreased resistance and stability under environmental stresses such as UV irradiation, oxidative stress, and heat. Further, cellular models confirmed its heightened sensitivity to environmental stresses. These data suggest that the R114C mutation impairs the hydrogen bond network and structural stability of βA3-crystallin, particularly at the boundary of the second Greek-key motif. This study revealed the pathological mechanism of βA3-R114C and may help in the development of potential treatment strategies for related cataracts.
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Affiliation(s)
- Silong Chen
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China
| | - Jiarui Guo
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China
| | - Wanyue Xu
- Hangzhou TCM Hospital Affiliated to Zhejiang Chinese Medical University, Hangzhou, Zhejiang 310053, China
| | - Hang Song
- Department of Ophthalmology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, China
| | - Jingjie Xu
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, 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, Hangzhou, Zhejiang Province 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.
| | - Yibo Yu
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China.
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2
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Lin N, Zhang Y, Song X, Xu J, Luo C, Tian Q, Yao K, Wu W, Chen X, Hu L. Cataract-causing mutations S78F and S78P of γD-crystallin decrease protein conformational stability and drive aggregation. Int J Biol Macromol 2023; 253:126910. [PMID: 37739288 DOI: 10.1016/j.ijbiomac.2023.126910] [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: 07/03/2023] [Revised: 08/28/2023] [Accepted: 09/13/2023] [Indexed: 09/24/2023]
Abstract
Congenital cataract is the leading cause of childhood blindness, which primarily results from genetic factors. γD-crystallin is the most abundant γ-crystallin and is essential for maintaining lens transparency and refractivity. Numerous mutations in γD-crystallin have been reported with unclear pathogenic mechanism. Two different cataract-causing mutations Ser78Phe and Ser78Pro in γD-crystallin were previously identified at the same conserved Ser78 residue. In this work, firstly, we purified the mutants and characterized for the structural change using fluorescence spectroscopy, circular dichroism (CD) spectroscopy, and size-exclusion chromatography (SEC). Both mutants were prone to form insoluble precipitates when expressed in Escherichia coli strain BL21 (DE3) cells. Compared with wild-type (WT), both mutations caused structural disruption, increased hydrophobic exposure, decreased solubility, and reduced thermal stability. Next, we investigated the aggregation of the mutants at the cellular level. Overexpression the mutants in HLE-B3 and HEK 293T cells could induce aggresome formations. The environmental stresses (including heat, ultraviolet irradiation and oxidative stress) promoted the formation of aggregates. Moreover, the intracellular S78F and S78P aggregates could be reversed by lanosterol. Molecular dynamic simulation indicated that both mutations disrupted the structural integrity of Greek-key motif 2. Hence, our results reveal the vital role of conserved Ser78 in maintaining the structural stability, which can offer new insights into the mechanism of cataract formation.
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Affiliation(s)
- Ningqin Lin
- Department of Nephrology, The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, Zhejiang Province, 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
| | - 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
| | - Xiaohui Song
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China
| | - Jingjie Xu
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China
| | - Chenqi Luo
- 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
| | - Ke Yao
- 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.
| | - 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
- Department of Nephrology, The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, Zhejiang Province, China.
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3
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Delas F, Koller S, Feil S, Dacheva I, Gerth-Kahlert C, Berger W. Novel CRYGC Mutation in Conserved Ultraviolet-Protective Tryptophan (p.Trp131Arg) Is Linked to Autosomal Dominant Congenital Cataract. Int J Mol Sci 2023; 24:16594. [PMID: 38068917 PMCID: PMC10706789 DOI: 10.3390/ijms242316594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2023] [Revised: 10/13/2023] [Accepted: 11/14/2023] [Indexed: 12/18/2023] Open
Abstract
Congenital cataract (CC), the most prevalent cause of childhood blindness and amblyopia, necessitates prompt and precise genetic diagnosis. The objective of this study is to identify the underlying genetic cause in a Swiss patient with isolated CC. Whole exome sequencing (WES) and copy number variation (CNV) analysis were conducted for variant identification in a patient born with a total binocular CC without a family history of CC. Sanger Sequencing was used to confirm the variant and segregation analysis was used to screen the non-affected parents. The first de novo missense mutation at c.391T>C was identified in exon 3 of CRYGC on chromosome 2 causing the substitution of a highly conserved Tryptophan to an Arginine located at p.Trp131Arg. Previous studies exhibit significant changes in the tertiary structure of the crystallin family in the following variant locus, making CRYGC prone to aggregation aggravated by photodamage resulting in cataract. The variant can be classified as pathogenic according to the American College of Medical Genetics and Genomics (ACMG) criteria (PP3 + PM1 + PM2 + PS2; scoring 10 points). The identification of this novel variant expands the existing knowledge on the range of variants found in the CRYGC gene and contributes to a better comprehension of cataract heterogeneity.
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Affiliation(s)
- Flora Delas
- Institute of Medical Molecular Genetics, University of Zurich, 8952 Schlieren, Switzerland; (F.D.); (S.K.); (S.F.)
| | - Samuel Koller
- Institute of Medical Molecular Genetics, University of Zurich, 8952 Schlieren, Switzerland; (F.D.); (S.K.); (S.F.)
| | - Silke Feil
- Institute of Medical Molecular Genetics, University of Zurich, 8952 Schlieren, Switzerland; (F.D.); (S.K.); (S.F.)
| | - Ivanka Dacheva
- Department of Ophthalmology, Cantonal Hospital of St. Gallen, 9007 St. Gallen, Switzerland;
| | | | - Wolfgang Berger
- Institute of Medical Molecular Genetics, University of Zurich, 8952 Schlieren, Switzerland; (F.D.); (S.K.); (S.F.)
- Neuroscience Center Zürich (ZNZ), University of Zurich and ETH Zurich, 8006 Zurich, Switzerland
- Zurich Center for Integrative Human Physiology (ZIHP), University of Zurich, 8006 Zurich, Switzerland
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4
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Greiner JV, Glonek T. Adenosine Triphosphate (ATP) and Protein Aggregation in Age-Related Vision-Threatening Ocular Diseases. Metabolites 2023; 13:1100. [PMID: 37887425 PMCID: PMC10609282 DOI: 10.3390/metabo13101100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Revised: 10/16/2023] [Accepted: 10/17/2023] [Indexed: 10/28/2023] Open
Abstract
Protein aggregation is the etiopathogenesis of the three most profound vision-threatening eye diseases: age-related cataract, presbyopia, and age-related macular degeneration. This perspective organizes known information on ATP and protein aggregation with a fundamental unrecognized function of ATP. With recognition that maintenance of protein solubility is related to the high intracellular concentration of ATP in cells, tissues, and organs, we hypothesize that (1) ATP serves a critical molecular function for organismal homeostasis of proteins and (2) the hydrotropic feature of ATP prevents pathological protein aggregation while assisting in the maintenance of protein solubility and cellular, tissue, and organismal function. As such, the metabolite ATP plays an extraordinarily important role in the prevention of protein aggregation in the leading causes of vision loss or blindness worldwide.
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Affiliation(s)
- Jack V. Greiner
- Schepens Eye Research Institute of Massachusetts Eye & Ear Infirmary, Boston, MA 02114, USA
- Department of Ophthalmology, Harvard Medical School, Boston, MA 02115, USA
- Clinical Eye Research of Boston, Boston, MA 01890, USA;
| | - Thomas Glonek
- Clinical Eye Research of Boston, Boston, MA 01890, USA;
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5
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Vendra VPR, Ostrowski C, Clark R, Dyba M, Tarasov SG, Hejtmancik JF. The Y46D Mutation Destabilizes Dense Packing of the Second Greek Key Pair of Human γC-Crystallin Causing Congenital Nuclear Cataracts. Biochemistry 2023; 62:1864-1877. [PMID: 37184593 PMCID: PMC10758276 DOI: 10.1021/acs.biochem.2c00628] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
The γ-crystallins are highly expressed structural lens proteins comprising four Greek key motifs arranged in two domains. Their globular structure and short-range spatial ordering are essential for lens transparency. Aromatic residues play a vital role in stabilizing Greek key folds by forming Greek key or non-Greek key pairs or tyrosine corners. We investigated the effects of the cataractogenic Y46D mutation in the second Greek key pair (Y46-Y51) of human γC-crystallin on its stability and aggregation. Wild-type and Y46D mutant human γC-crystallin were overexpressed in E. coli BL-21(DE3) PLysS cells, purified using ion-exchange and size-exclusion chromatography, and analyzed by fluorescence spectroscopy and circular dichroism spectroscopy. The Y46D mutation does not affect the γC-crystallin backbone conformation under benign conditions but alters the tryptophan microenvironment, exposing hydrophobic residues to the surface. The Y46D mutant undergoes a three-state transition under thermal stress with midpoints of 54.6 and 67.7 °C while the wild type shows a two-state transition with a midpoint of 77.6 °C. The Y46D mutant also shows a three-state transition under GuHCl stress with Cm values of 0.9 and 2.1 M while the wild type shows a two-state transition with a Cm of 2.4 M GuHCl. Mutant but not wild-type γC-crystallin forms light scattering particles upon heating at 65 °C. Overall, the Y46D CRYGS mutation leaves the protein fold intact under benign conditions but destabilizes the molecule by altering the tryptophan microenvironment and exposing hydrophobic residues to its surface, thus increasing its susceptibility to thermal and chemical stress with resultant self-aggregation, light scattering, and cataract.
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Affiliation(s)
- Venkata Pulla Rao Vendra
- Ophthalmic Molecular Genetics Section, Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20852, United States
| | - Christian Ostrowski
- Ophthalmic Molecular Genetics Section, Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20852, United States
| | - Rebecca Clark
- Ophthalmic Molecular Genetics Section, Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20852, United States
| | - Marzena Dyba
- Biophysics Resource in the Center for Structural Biology, National Cancer Institute, National Institutes of Health, Frederick, Maryland 21702-4091, United States
| | - Sergey G Tarasov
- Biophysics Resource in the Center for Structural Biology, National Cancer Institute, National Institutes of Health, Frederick, Maryland 21702-4091, United States
| | - J Fielding Hejtmancik
- Ophthalmic Molecular Genetics Section, Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20852, United States
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6
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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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7
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Aguayo-Ortiz R, Guzmán-Ocampo DC, Dominguez L. Insights into the binding of morin to human γD-crystallin. Biophys Chem 2021; 282:106750. [PMID: 34999344 DOI: 10.1016/j.bpc.2021.106750] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 12/19/2021] [Accepted: 12/21/2021] [Indexed: 11/28/2022]
Abstract
Crystallin aggregation in the eye lens is one of the leading causes of cataract formation. The increase in the human γD-crystallin (HγDC) aggregation propensity has been associated with the oligomerization of its partially folded and fully unfolded structure. A recent study demonstrated that the binding of flavonoid morin (MOR) to HγDC inhibits the fibrillation of this protein. In this work, we carry out an exhaustive search for the possible binding site of MOR on HγDC by combining an ensemble docking approach with the Wrap 'N' Shake protocol. In agreement with previous results, we found a potential MOR-binding site in the cleft formed between the N-terminal and C-terminal domains of HγDC. MOR preference for the cleft residues was observed even with the interface-opened intermediate conformers of HγDC. In addition, metadynamics simulations were carried out to corroborate the stabilizing activity of MOR on HγDC structure and to identify the structural regions implicated during the unfolding inhibition. Overall, this study provides relevant insights into the identification of new HγDC aggregation inhibitors.
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Affiliation(s)
- Rodrigo Aguayo-Ortiz
- Departamento de Farmacia, Facultad de Química, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico
| | - Dulce C Guzmán-Ocampo
- Departamento de Fisicoquímica, Facultad de Química, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico
| | - Laura Dominguez
- Departamento de Fisicoquímica, Facultad de Química, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico.
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8
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Xu J, Wang H, Wu C, Wang A, Wu W, Xu J, Luo C, Ni S, Yao K, Chen X. Pathogenic mechanism of congenital cataract caused by the CRYBA1/A3-G91del variant and related intervention strategies. Int J Biol Macromol 2021; 189:44-52. [PMID: 34419537 DOI: 10.1016/j.ijbiomac.2021.08.111] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2021] [Revised: 08/13/2021] [Accepted: 08/14/2021] [Indexed: 10/20/2022]
Abstract
Congenital cataracts, which are genetically heterogeneous eye disorders, lead to visual impairment in childhood. In our previous study, we identified a novel mutation in exon 4 of the CRYBA1/BA3 gene, which resulted in the deletion of a highly conserved glycine at codon 91 (G91del) and perinuclear zonular cataract. The G91del variant is one of the most frequent pathogenic mutations in CRYBA1/BA3; however, its pathogenic mechanism remains unclear. In this study, we purified βA3-crystallin and the βA3-G91del variant. βA3-G91del was prone to proteolysis and exhibited very low solubility and low structural stability. Next, we constructed a CRYBA1/BA3 mutant cell model and observed that G91del mutant proteins were more sensitive to environmental stress and prone to form aggregates. Size-exclusion chromatography and molecular dynamics simulation showed that the G91del mutation impaired the ability of βA3 to form homo-oligomers. In addition, the protein folding process of βA3-G91del was complicated and showed more intermediate states, resulting in amyloid fiber aggregation and induction of cellular apoptosis. Finally, we investigated intervention strategies for congenital cataract caused by the CRYBA1/A3-G91del variant. The addition of lanosterol reversed the negative effects of the G91del mutation under external stress. This study may help explore potential treatment strategies for related cataracts.
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Affiliation(s)
- Jingjie Xu
- 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
| | - Chengpeng Wu
- 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
| | - Ailing 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
| | - Jia Xu
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China
| | - Chenqi Luo
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou 310009, China
| | - Shuang Ni
- 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.
| | - 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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9
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Shiels A, Hejtmancik JF. Inherited cataracts: Genetic mechanisms and pathways new and old. Exp Eye Res 2021; 209:108662. [PMID: 34126080 PMCID: PMC8595562 DOI: 10.1016/j.exer.2021.108662] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 05/13/2021] [Accepted: 06/01/2021] [Indexed: 12/15/2022]
Abstract
Cataract(s) is the clinical equivalent of lens opacity and is caused by light scattering either by high molecular weight protein aggregates in lens cells or disruption of the lens microarchitecture itself. Genetic mutations underlying inherited cataract can provide insight into the biological processes and pathways critical for lens homeostasis and transparency, classically including the lens crystallins, connexins, membrane proteins or components, and intermediate filament proteins. More recently, cataract genes have been expanded to include newly identified biological processes such as chaperone or protein degradation components, transcription or growth factors, channels active in the lens circulation, and collagen and extracellular matrix components. Cataracts can be classified by age, and in general congenital cataracts are caused by severe mutations resulting in major damage to lens proteins, while age related cataracts are associated with variants that merely destabilize proteins thereby increasing susceptibility to environmental insults over time. Thus there might be separate pathways to opacity for congenital and age-related cataracts whereby congenital cataracts induce the unfolded protein response (UPR) and apoptosis to destroy the lens microarchitecture, while in age related cataract high molecular weight (HMW) aggregates formed by denatured crystallins bound by α-crystallin result in light scattering without severe damage to the lens microarchitecture.
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Affiliation(s)
- Alan Shiels
- Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, MO, 63110, USA.
| | - J Fielding Hejtmancik
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, MD, 20892-1860, USA.
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10
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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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11
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Fu C, Xu J, Yang X, Chen X, Yao K. Cataract-causing mutations L45P and Y46D impair the thermal stability of γC-crystallin. Biochem Biophys Res Commun 2021; 539:70-76. [PMID: 33422942 DOI: 10.1016/j.bbrc.2020.12.096] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Accepted: 12/28/2020] [Indexed: 10/22/2022]
Abstract
Crystallin gene mutations are responsible for about half of the congenital cataract caused by genetic disorders. L45P and Y46D mutations of γC-crystallin have been reported in patients with nuclear congenital cataract. In this study, we explored the thermal stability of wild type (WT), L45P, and Y46D mutants of γC-crystallin at low and high concentrations, as well as the effect of αA-crystallin on the thermal stability of mutants. Spectroscopic experiments were used to monitor the structural changes on temperature-gradient and time-course heating process. Intermediate morphologies were determined through cryo-electron microscopy. The thermal stability of WT and mutants at concentrations ranging up to hundreds of milligrams were assessed via the UNcle multifunctional protein stability analysis system. The results showed that L45P and Y46D mutations impaired the thermal stability of γC-crystallin at low (0.2 mg/mL) and high concentrations (up to 200 mg/mL). Notably, with increase in protein concentration, the thermal stability of L45P and Y46D mutants of γC-crystallin simultaneously decreased. Thermal stability of L45P and Y46D mutants could be rescued by αA-crystallin in a concentration-dependent manner. The dramatic decrease in thermal stability of γC-crystallin caused by L45P and Y46D mutations contributed to congenital cataract in the mature human lens.
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Affiliation(s)
- Chenxi Fu
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou, 310009, China
| | - Jingjie Xu
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou, 310009, China
| | - Xiaoxia Yang
- 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.
| | - Ke Yao
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou, 310009, China.
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12
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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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13
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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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Xu J, Wang H, Wang A, Xu J, Fu C, Jia Z, Yao K, Chen X. βB2 W151R mutant is prone to degradation, aggregation and exposes the hydrophobic side chains in the fourth Greek Key motif. Biochim Biophys Acta Mol Basis Dis 2020; 1867:166018. [PMID: 33246011 DOI: 10.1016/j.bbadis.2020.166018] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2020] [Revised: 11/14/2020] [Accepted: 11/16/2020] [Indexed: 12/16/2022]
Abstract
Studies have established that congenital cataract is the major cause of blindness in children across the globe. The β-crystallin protein family is the richest and most soluble structural protein in the lens. Their solubility and stability are essential in maintaining lens transparency. In this study, we identified a novel βB2 mutation W151R in a rare progressive cortical congenital cataract family and explored its pathogenesis using purified protein and mutant related cataract-cell models. Due to its low solubility and poor structural stability, the βB2 W151R mutation was prone to aggregation. Moreover, the W151R mutation enhanced the exposure of the hydrophobic side chains in the fourth Greek Key motif, which were readily degraded by trypsin. However, upon the administration of lanosterol, the negative effect of the W151R mutation was reversed. Therefore, lanosterol is a potential therapeutic option for cataracts.
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Affiliation(s)
- Jingjie Xu
- Eye Center of the Second Affiliated Hospital, Medical College of Zhejiang University, 88 Jiefang Road, Hangzhou 310009, China
| | - Huaxia Wang
- Institute of Translational Medicine, Zhejiang University School of Medicine, Hangzhou 310020, China
| | - Ailing Wang
- Institute of Translational Medicine, Zhejiang University School of Medicine, Hangzhou 310020, China
| | - Jia Xu
- Eye Center of the Second Affiliated Hospital, Medical College of Zhejiang University, 88 Jiefang Road, Hangzhou 310009, China
| | - Chenxi Fu
- Eye Center of the Second Affiliated Hospital, Medical College of Zhejiang University, 88 Jiefang Road, Hangzhou 310009, China
| | - Zhekun Jia
- Eye Center of the Second Affiliated Hospital, Medical College of Zhejiang University, 88 Jiefang Road, Hangzhou 310009, China
| | - Ke Yao
- Eye Center of the Second Affiliated Hospital, Medical College of Zhejiang University, 88 Jiefang Road, Hangzhou 310009, China.
| | - Xiangjun Chen
- Eye Center of the Second Affiliated Hospital, Medical College of Zhejiang University, 88 Jiefang Road, Hangzhou 310009, China; Institute of Translational Medicine, Zhejiang University School of Medicine, Hangzhou 310020, China.
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15
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Abstract
Cataracts, the leading cause of vision impairment worldwide, arise from abnormal aggregation of lens proteins. According to the World Health Organization, cataracts cause more than 40% of blindness cases. As the population ages, the prevalence of cataracts will increase rapidly. Although cataract surgery is regarded as effective, it still suffers from complications and high cost, and could not meet the increasingly surgery demand. Therefore, pharmacological treatment for cataracts is a cheaper and more readily available option for patients, which is also a hot topic for years. Anti-cataract drug screening was previously mainly based on the specific pathogenic factors: oxidative stress, excess of quinoid substances, and aldose reductase (AR) activation. And several anti-cataract drugs have been applied in the clinic, while the effect is still unsatisfied. Makley and Zhao recently identified two kinds of novel pharmacological substances (25-hydroxycholesterol, lanosterol) that can reverse lens opacity by dissolving the aggregation of crystallin proteins, indicating that protein aggregation is not an endpoint and could be reversed with specific small-molecule drugs, significantly boosting the development of the cataract pharmacopeia and being regarded as a new dawn for cataract treatment. Our team built a novel optimized platform and had screened several potential therapeutic agents from a collection of lanosterol derivatives. In this review, we would mainly focus on the advancement of cataract pharmacotherapy based on the targets for anti-cataract drugs.
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Affiliation(s)
- Jingjie Xu
- Eye Center of the Second Affiliated Hospital, Medical College of Zhejiang University, Hangzhou, China
| | - Qiuli Fu
- Eye Center of the Second Affiliated Hospital, Medical College of Zhejiang University, Hangzhou, China
| | - Xiangjun Chen
- Eye Center of the Second Affiliated Hospital, Medical College of Zhejiang University, Hangzhou, China.,Institute of Translational Medicine, Zhejiang University School of Medicine, Hangzhou, China
| | - Ke Yao
- Eye Center of the Second Affiliated Hospital, Medical College of Zhejiang University, Hangzhou, China
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16
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Ji Y, Zhao X, Zhang J, Zhang D, Tian C, Zhang L, Zhao Y, Zhao J. A novel missense mutation of CRYBB1 causes congenital cataract in a Chinese family. Eur J Ophthalmol 2020; 31:1064-1069. [PMID: 32223445 DOI: 10.1177/1120672120914497] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
OBJECTIVE OF THE STUDY To identify the pathogenic gene and mutation site of a Chinese family with congenital cataract. METHODS Eight family members and 100 controls were employed, and targeted exome sequencing was used to identify the genetically pathogenic factor of the proband. RESULTS Targeted next-generation sequencing identified a novel missense mutation c.209A>C (p.Q70P) of CRYBB1 gene in the family. Sanger sequencing results showed that this heterozygous mutation was a causative mutation, which was not found in unaffected family members and healthy controls. Bioinformatics predicts that the effect of this mutation on protein function is probably harmful. CONCLUSION We demonstrate that c.209A>C of CRYBB1 gene is a pathogenic mutation in the family of congenital nuclear cataract in this study. This is the first report that this mutation leads to congenital nuclear cataract, which broadens the mutation spectrum of CRYBB1 gene in congenital nuclear cataract.
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Affiliation(s)
- Yanan Ji
- Medical College, Qingdao University, Qingdao, China
| | - Xiangyu Zhao
- Department of Medical Genetics, Linyi People's Hospital, Linyi, China
| | - Juanmei Zhang
- Department of Ophthalmology, Linyi People's Hospital, Linyi, China
| | - Dan Zhang
- Medical College, Qingdao University, Qingdao, China
| | - Chunliu Tian
- Medical College, Qingdao University, Qingdao, China
| | - Linlin Zhang
- Medical College, Qingdao University, Qingdao, China
| | | | - Jun Zhao
- Department of Ophthalmology, Linyi People's Hospital, Linyi, China
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Aguayo-Ortiz R, Dominguez L. Effects of Mutating Trp42 Residue on γD-Crystallin Stability. J Chem Inf Model 2020; 60:777-785. [PMID: 31747273 DOI: 10.1021/acs.jcim.9b00747] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Oligomerization and aggregation of γD-crystallins (HγDC) in the eye lens is one of the main causes of cataract development. To date, several congenital mutations related to this protein are known to promote the formation of aggregates. Previous studies have demonstrated that mutations in W42 residue of HγDC lead to the generation of partially unfolded intermediates that are more prone to aggregate. To understand the role of W42 in the stability of HγDC, we performed alchemical free-energy calculations and all-atom molecular dynamics simulations of different W42 mutant models. Our results suggest that substitution of W42 by small size and/or polar residues promotes HγDC denaturation due to the entry of water molecules into the hydrophobic core of the N-terminal domain. Similar behavior was observed in the C-terminal domain of HγDC when mutating the W130 residue located in a homologous position. Moreover, the exposure of the hydrophobic core residues could lead to the formation of aggregation-prone partially unfolded species. Overall, this study takes a step toward understanding the role of HγDC in cataract development.
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Affiliation(s)
- Rodrigo Aguayo-Ortiz
- Facultad de Química, Departamento de Fisicoquímica , Universidad Nacional Autónoma de México , Mexico City 04510 , Mexico.,Center for Arrhythmia Research, Department of Internal Medicine, Division of Cardiovascular Medicine , University of Michigan , Ann Arbor , Michigan 48109 , United States
| | - Laura Dominguez
- Facultad de Química, Departamento de Fisicoquímica , Universidad Nacional Autónoma de México , Mexico City 04510 , Mexico
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18
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Molecular genetics of congenital cataracts. Exp Eye Res 2019; 191:107872. [PMID: 31770519 DOI: 10.1016/j.exer.2019.107872] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 11/12/2019] [Accepted: 11/13/2019] [Indexed: 12/18/2022]
Abstract
Congenital cataracts, the most common cause of visual impairment and blindness in children worldwide, have diverse etiologies. According to statistics analysis, about one quarter of congenital cataracts caused by genetic defects. Various mutations of more than one hundred genes have been identified in hereditary cataracts so far. In this review, we briefly summarize recent developments about the genetics, molecular mechanisms, and treatments of congenital cataracts. The studies of these pathogenic mutations and molecular genetics is making it possible for us to comprehend the underlying mechanisms of cataractogenesis and providing new insights into the preventive, diagnostic and therapeutic approaches of cataracts.
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19
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Abstract
Cataract, the clinical correlate of opacity or light scattering in the eye lens, is usually caused by the presence of high-molecular-weight (HMW) protein aggregates or disruption of the lens microarchitecture. In general, genes involved in inherited cataracts reflect important processes and pathways in the lens including lens crystallins, connexins, growth factors, membrane proteins, intermediate filament proteins, and chaperones. Usually, mutations causing severe damage to proteins cause congenital cataracts, while milder variants increasing susceptibility to environmental insults are associated with age-related cataracts. These may have different pathogenic mechanisms: Congenital cataracts induce the unfolded protein response and apoptosis. By contrast, denatured crystallins in age-related cataracts are bound by α-crystallin and form light-scattering HMW aggregates. New therapeutic approaches to age-related cataracts use chemical chaperones to solubilize HMW aggregates, while attempts are being made to regenerate lenses using endogenous stem cells to treat congenital cataracts.
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Affiliation(s)
- Alan Shiels
- Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri 63110, USA;
| | - J Fielding Hejtmancik
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892-1860, USA;
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20
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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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21
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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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22
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Song Z, Si N, Xiao W. A novel mutation in the CRYAA gene associated with congenital cataract and microphthalmia in a Chinese family. BMC MEDICAL GENETICS 2018; 19:190. [PMID: 30340470 PMCID: PMC6194747 DOI: 10.1186/s12881-018-0695-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Accepted: 09/24/2018] [Indexed: 11/10/2022]
Abstract
Background Congenital cataract is the leading cause of blindness in children worldwide. Approximately half of all congenital cataracts have a genetic basis. Protein aggregation is the single most important factor in cataract formation. Methods A four-generation Chinese family diagnosed with autosomal dominant congenital cataracts and microphthalmia was recruited at the Shengjing Hospital of China Medical University. Genomic DNA was extracted from the peripheral blood of the participants. All coding exons and flanking regions of seven candidate genes (CRYAA, CRYBA4, CRYBB2, CRYGC, GJA8, MAF, and PITX3) were amplified and sequenced. Restriction fragment length polymorphism (RFLP) assays were performed to confirm the candidate causative variant, c.35G > T in the CRYAA gene. We constructed pcDNA3.1(+)-CRYAA expression plasmids containing either the wild-type or the R12L mutant alleles and respectively transfected them into HEK293T cells and into HeLa cells. Western blotting was performed to determine protein expression levels and protein solubility. Immunofluorescence was performed to determine protein sub-cellular localization. Results A heterozygous variant c.35G > T was identified in exon 1 of CRYAA, which resulted in a substitution of arginine to leucine at codon 12 (p.R12L). The nucleotide substitution c.35G > T was co-segregated with the disease phenotype in the family. The mutant R12L-CRYAA in HEK293T cells showed a significant increase in the expression level of the CRYAA protein compared with the wild-type cells. Moreover, a large amount of the mutant protein aggregated in the precipitate where the wild-type protein was not detected. Immunofluorescence studies showed that the overexpressed mutant CRYAA in HeLa cells formed large cytoplasmic aggregates and aggresomes. Conclusions In summary, we described a case of human congenital cataract and microphthalmia caused by a novel mutation in the CRYAA gene, which substituted an arginine at position 12 in the N-terminal region of αA-crystallin. The molecular mechanisms that underlie the pathogenesis of human congenital cataract may be characterized by the prominent effects of the p.R12L mutation on αA-crystallin aggregation and solubility. Our study also expands the spectrum of known CRYAA mutations.
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Affiliation(s)
- Zixun Song
- Department of Ophthalmology, Shengjing Hospital, China Medical University, Shenyang, 110004, Liaoning, China
| | - Nuo Si
- McKusick-Zhang Center for Genetic Medicine, Institute of Basic Medical Sciences Chinese Academy of Medical Sciences, School of Basic Medicine Peking Union Medical College, Beijing, 100005, China
| | - Wei Xiao
- Department of Ophthalmology, Shengjing Hospital, China Medical University, Shenyang, 110004, Liaoning, China.
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23
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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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24
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Xu J, Zhao WJ, Chen XJ, Yao K, Yan YB. Introduction of an extra tryptophan fluorophore by cataract-associating mutations destabilizes βB2-crystallin and promotes aggregation. Biochem Biophys Res Commun 2018; 504:851-856. [DOI: 10.1016/j.bbrc.2018.09.028] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2018] [Accepted: 09/06/2018] [Indexed: 12/18/2022]
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25
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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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26
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Shiels A, Hejtmancik JF. Mutations and mechanisms in congenital and age-related cataracts. Exp Eye Res 2017; 156:95-102. [PMID: 27334249 PMCID: PMC5538314 DOI: 10.1016/j.exer.2016.06.011] [Citation(s) in RCA: 146] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Revised: 06/09/2016] [Accepted: 06/16/2016] [Indexed: 01/06/2023]
Abstract
The crystalline lens plays an important role in the refractive vision of vertebrates by facilitating variable fine focusing of light onto the retina. Loss of lens transparency, or cataract, is a frequently acquired cause of visual impairment in adults and may also present during childhood. Genetic studies have identified mutations in over 30 causative genes for congenital or other early-onset forms of cataract as well as several gene variants associated with age-related cataract. However, the pathogenic mechanisms resulting from genetic determinants of cataract are only just beginning to be understood. Here, we briefly summarize current concepts pointing to differences in the molecular mechanisms underlying congenital and age-related forms of cataract.
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Affiliation(s)
- Alan Shiels
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - J Fielding Hejtmancik
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, MD 20892-1860, USA.
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27
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Congenital microcornea-cataract syndrome-causing mutation X253R increases βB1-crystallin hydrophobicity to promote aggregate formation. Biochem J 2016; 473:2087-96. [DOI: 10.1042/bcj20160247] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2016] [Accepted: 05/10/2016] [Indexed: 01/12/2023]
Abstract
The high solubility and lifelong stability of crystallins are crucial to the maintenance of lens transparency and optical properties. Numerous crystallin mutations have been linked to congenital cataract, which is one of the leading causes of newborn blindness. Besides cataract, several crystallin mutations have also been linked to syndromes such as congenital microcornea-cataract syndrome (CMCC). However, the molecular mechanism of CMCC caused by crystallin mutations remains elusive. In the present study, we investigated the mechanism of CMCC caused by the X253R mutation in βB1-crystallin. The exogenously expressed X253R proteins were prone to form p62-negative aggregates in HeLa cells, strongly inhibited cell proliferation and induced cell apoptosis. The intracellular X253R aggregates could be successfully redissolved by lanosterol but not cholesterol. The extra 26 residues at the C-terminus of βB1-crystallin introduced by the X253R mutation had little impact on βB1-crystallin structure and stability, but increased βB1-crystallin hydrophobicity and decreased its solubility. Interestingly, the X253R mutant fully abolished the aggregatory propensity of βB1- and βA3/βB1-crystallins at high temperatures, suggesting that X253R was an aggregation-inhibition mutation of β-crystallin homomers and heteromers in dilute solutions. Our results suggest that an increase in hydrophobicity and a decrease in solubility might be responsible for cataractogenesis induced by the X253R mutation, while the cytotoxic effect of X253R aggregates might contribute to the defects in ocular development. Our results also highlight that, at least in some cases, the aggregatory propensity in dilute solutions could not fully mimic the behaviours of mutated proteins in the crowded cytoplasm of the cells.
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Qi LB, Hu LD, Liu H, Li HY, Leng XY, Yan YB. Cataract-causing mutation S228P promotes βB1-crystallin aggregation and degradation by separating two interacting loops in C-terminal domain. Protein Cell 2016; 7:501-15. [PMID: 27318838 PMCID: PMC4930773 DOI: 10.1007/s13238-016-0284-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Accepted: 05/04/2016] [Indexed: 01/02/2023] Open
Abstract
β/γ-Crystallins are predominant structural proteins in the cytoplasm of lens fiber cells and share a similar fold composing of four Greek-key motifs divided into two domains. Numerous cataract-causing mutations have been identified in various β/γ-crystallins, but the mechanisms underlying cataract caused by most mutations remains uncharacterized. The S228P mutation in βB1-crystallin has been linked to autosomal dominant congenital nuclear cataract. Here we found that the S228P mutant was prone to aggregate and degrade in both of the human and E. coli cells. The intracellular S228P aggregates could be redissolved by lanosterol. The S228P mutation modified the refolding pathway of βB1-crystallin by affecting the formation of the dimeric intermediate but not the monomeric intermediate. Compared with native βB1-crystallin, the refolded S228P protein had less packed structures, unquenched Trp fluorophores and increased hydrophobic exposure. The refolded S228P protein was prone to aggregate at the physiological temperature and decreased the protective effect of βB1-crystallin on βA3-crystallin. Molecular dynamic simulation studies indicated that the mutation decreased the subunit binding energy and modified the distribution of surface electrostatic potentials. More importantly, the mutation separated two interacting loops in the C-terminal domain, which shielded the hydrophobic core from solvent in native βB1-crystallin. These two interacting loops are highly conserved in both of the N- and C-terminal domains of all β/γ-crystallins. We propose that these two interacting loops play an important role in the folding and structural stability of β/γ-crystallin domains by protecting the hydrophobic core from solvent access.
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Affiliation(s)
- Liang-Bo Qi
- State Key Laboratory of Membrane Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Li-Dan Hu
- State Key Laboratory of Membrane Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Huihui Liu
- State Key Laboratory of Membrane Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Hai-Yun Li
- State Key Laboratory of Membrane Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Xiao-Yao Leng
- State Key Laboratory of Membrane Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Yong-Bin Yan
- State Key Laboratory of Membrane Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China.
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