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Xu W, Chen J, Chen F, Wu W, Lin N, Guo Y, Hu L, Chen X. A novel cataract-related mutation R10P in γA-crystallin increases susceptibility to thermal shock and ultraviolet radiation of γA-crystallin. Biochem Biophys Res Commun 2024; 739:150585. [PMID: 39186870 DOI: 10.1016/j.bbrc.2024.150585] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2024] [Revised: 08/02/2024] [Accepted: 08/20/2024] [Indexed: 08/28/2024]
Abstract
Congenital cataract is one of the most common causes of childhood blindness, typically resulting from genetic mutations. Over a hundred gene mutations associated with congenital cataract have been identified, with approximately half occurring in the Crystallin genes. In this study, we identified a novel γA-crystallin pathogenic mutation (c. 29G > C, p. Arg10Pro (R10P)), from a four-generation Chinese family with congenital cataract, and investigated its potential molecular mechanisms underlying congenital cataracts. We compared the protein structure and stability of purified the wild type (WT) and R10P under physiological conditions and environmental stresses (UV irradiation, pH imbalance, heat shock, and chemical denaturation) using spectroscopic experiments, SEC analysis, and the UNcle protein analysis system. The results demonstrate that γA-R10P has no significant impact on the structure of γA-crystallin on normal condition. However, it is more sensitive to UV irradiation at high concentrations and prone to aggregation at high temperatures. Therefore, our study reveals the crucial role of the conserved site mutation R10P in maintaining protein structure and stability, providing new insights into the mechanisms of cataract formation.
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Affiliation(s)
- Wanyue Xu
- Hangzhou TCM Hospital Affiliated to Zhejiang Chinese Medical University, Hangzhou, Zhejiang, 310053, China
| | - Jing Chen
- Hangzhou TCM Hospital Affiliated to Zhejiang Chinese Medical University, Hangzhou, Zhejiang, 310053, China
| | - Fanrui Chen
- Gansu Key Laboratory of Biomonitoring and Bioremediation for Environmental Pollution, School of Life Sciences, Lanzhou University, Lanzhou, 730000, China
| | - Wei Wu
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou, 310009, China
| | - Ningqin Lin
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou, 310009, China; Institute of Translational Medicine, Zhejiang University School of Medicine, 268 Kaixuan Road, Hangzhou, 310020, China
| | - Yan Guo
- Hangzhou TCM Hospital Affiliated to Zhejiang Chinese Medical University, Hangzhou, Zhejiang, 310053, China
| | - Lidan Hu
- The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, 310052, China.
| | - Xiangjun Chen
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou, 310009, China; Institute of Translational Medicine, Zhejiang University School of Medicine, 268 Kaixuan Road, Hangzhou, 310020, China.
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2
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Sharma S, Deep S. Inhibition of fibril formation by polyphenols: molecular mechanisms, challenges, and prospective solutions. Chem Commun (Camb) 2024; 60:6717-6727. [PMID: 38835221 DOI: 10.1039/d4cc00822g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2024]
Abstract
Fibril formation is a key feature in neurodegenerative diseases like Alzheimer's, Parkinson's, and systemic amyloidosis. Polyphenols, found in plant-based foods, show promise in inhibiting fibril formation and disrupting disease progression. The ability of polyphenols to break the amyloid fibrils of many disease-linked proteins has been tested in numerous studies. Polyphenols have their distinctive mechanism of action. They behave differently on various events in the aggregation pathway. Their action also differs for different proteins. Some polyphenols only inhibit the formation of fibrils whereas others break the preformed fibrils. Some break the fibrils into smaller species, and some change them to other morphologies. This article delves into the intricate molecular mechanisms underlying the inhibitory effects of polyphenols on fibrillogenesis, shedding light on their interactions with amyloidogenic proteins and the disruption of fibril assembly pathways. However, addressing the challenges associated with solubility, stability, and bioavailability of polyphenols is crucial. The current strategies involve nanotechnology to improve the solubility and bioavailability, thus showing the potential to enhance the efficacy of polyphenols as therapeutics. Advancements in structural biology, computational modeling, and biophysics have provided insights into polyphenol-fibril interactions, offering hope for novel therapies for neurodegenerative diseases and amyloidosis.
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Affiliation(s)
- Shilpa Sharma
- Department of Chemistry and Biochemistry, University of Wisconsin, Milwaukee, Wisconsin, USA
| | - Shashank Deep
- Department of Chemistry, Indian Institute of Technology Delhi, New Delhi, India.
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3
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Goswami V, Tomar VR, Yashika, Deep S. Nanocarriers for the Delivery of Quercetin to Inhibit the UV-Induced Aggregation of γD-Crystallin. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:5617-5631. [PMID: 38051761 DOI: 10.1021/acs.langmuir.3c01910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/07/2023]
Abstract
Due to gradual environmental changes like ozone layer depletion and global warming, human eyes are exposed to UV light. Exposure to UV light can be a cause of cataracts, one of the ocular diseases that may cause vision impairment. To date, lens replacement has been the only treatment available for cataracts. In our present study, we carried out an extensive examination of polyphenols as inhibitors for UV-induced aggregation of γD-crystallin. On exposure to UV-C light, γD-crystallin forms fibrils instead of amorphous aggregates. Various polyphenols were tested as inhibitors; out of them, quercetin, baicalein, and caffeic acid were found to be effective. As polyphenols are insoluble in water, nanoencapsulation was used to enhance their bioavailability. CS-TPP and CS-PLGA encapsulating systems were considered, as they form biodegradable nanocapsules. Out of three polyphenols (quercetin, baicalein, and caffeic acid), quercetin forms nanocarriers of smaller sizes, a must for crossing the retinal barrier. Quercetin nanocarriers were considered an effective system that could be used for therapeutic applications. For these nanocarriers, encapsulation efficiency and polyphenol release kinetics were studied. CS-PLGA NPs were found to have a better loading efficiency for quercetin than CS-TPP NPs.
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Affiliation(s)
- Vishakha Goswami
- Department of Chemistry, Indian Institute of Technology, Hauzkhas, Delhi New Delhi 110016, India
| | - Vijay Raj Tomar
- Department of Chemistry, Indian Institute of Technology, Hauzkhas, Delhi New Delhi 110016, India
| | - Yashika
- Department of Chemistry, Indian Institute of Technology, Hauzkhas, Delhi New Delhi 110016, India
| | - Shashank Deep
- Department of Chemistry, Indian Institute of Technology, Hauzkhas, Delhi New Delhi 110016, India
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4
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Ghosh D, Sojitra KA, Biswas A, Agarwal M, Radhakrishna M. Effect of mutations on the folding and stability of γD-crystallin protein. J Biomol Struct Dyn 2023:1-15. [PMID: 37830785 DOI: 10.1080/07391102.2023.2266768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Accepted: 09/25/2023] [Indexed: 10/14/2023]
Abstract
Interprotein interactions between the partially unfolded states of γD-crystallin (γD-crys) protein are known to cause cataracts. Therefore, understanding the unfolding pathways of native γD-crys is extremely crucial to delineate their aggregation mechanism. In this study, we have performed extensive all-atom Molecular Dynamics simulations with explicit solvent to understand the role of the critical residues that drive the stability of the motifs and domains of γD-crys in its wild type and mutant forms. Our findings show that while the individual motifs of wild type are not stable in the native form, the individual domains remain structurally stable at 425K. This enhanced stability of the domain was attributed to the hydrophobic interactions between the motifs. Single and double point mutations of the domains with negatively charged aspartic and glutamic acid amino acid residues (I3E, W42D, W42E, I3D/W42D, I3E/W42E, and L92D/W157D) decreases the structural stability, leading to unfolding of individual domains of γD-crys. We believe that our study sheds light on the weakest links of γD-crys, along with the role of interactions stabilizing the domains. Further, this study bolsters and provides a better understanding of the domain swapping mechanism of aggregation of γD-crys.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Deepshikha Ghosh
- Department of Biological Sciences and Engineering, Indian Institute of Technology (IIT), Gandhinagar, Palaj, Gujarat, India
| | - Kandarp Ashokbhai Sojitra
- Replace with:Department of Chemical Engineering, Indian Institute of Technology (IIT) Gandhinagar, Palaj, Gujarat, India
| | - Anushka Biswas
- Replace with:Department of Chemical Engineering, Indian Institute of Technology (IIT) Gandhinagar, Palaj, Gujarat, India
| | - Manish Agarwal
- Computer Services Centre, Indian Institute of Technology (IIT) Delhi, Hauz Khas, New Delhi, Delhi
| | - Mithun Radhakrishna
- Replace with:Department of Chemical Engineering, Indian Institute of Technology (IIT) Gandhinagar, Palaj, Gujarat, India
- Center for Biomedical Engineering, Indian Institute of Technology (IIT) Gandhinagar, Palaj, Gujarat, India
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5
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Honisch C, Rodella U, Gatto C, Ruzza P, Tóthová JD. Oxidative Stress and Antioxidant-Based Interventional Medicine in Ophthalmology. Pharmaceuticals (Basel) 2023; 16:1146. [PMID: 37631061 PMCID: PMC10458870 DOI: 10.3390/ph16081146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 08/07/2023] [Accepted: 08/10/2023] [Indexed: 08/27/2023] Open
Abstract
The different anatomical compartments of the eye are highly subjected to reactive oxygen species (ROS) generation due to internal factors, such as metabolic high oxygen consumption, as well as environmental factors, including UV light. An antioxidant defense system is endowed in the eye tissues to regulate ROS quantity and activity. When this homeostatic system is overwhelmed, oxidative stress occurs, causing cellular damage, chronic inflammation, and tissue degeneration. It also plays a significant role in the development and progression of various ocular diseases. Understanding the mechanisms underlying oxidative stress in ocular conditions is thus crucial for the development of effective prevention and treatment strategies. To track marketed products based on antioxidant substances as active ingredients, the databases of the European Medicines Agency and the U.S. Food and Drug Administration were consulted. Only a limited number of items were identified, which were either used as therapeutic treatment or during ocular surgery, including antioxidants, synthetical derivatives, or pro-drugs designed to enhance tissue permeation and activity. This review aims to provide an overview of the primary ocular pathologies associated with oxidative stress and of the available pharmacological interventions centered around antioxidant molecules. Such insights are essential for advancing the development of effective prevention and novel treatment approaches.
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Affiliation(s)
- Claudia Honisch
- Institute of Biomolecular Chemistry of CNR (ICB-CNR), Via F. Marzolo, 1, 35131 Padova, Italy;
| | - Umberto Rodella
- Research and Development, AL.CHI.MI.A. S.R.L., Viale Austria, 14, 35020 Ponte San Nicolờ, Italy; (U.R.); (C.G.)
- Fondazione Banca degli Occhi del Veneto (FBOV), Via Paccagnella, 11, 30174 Zelarino, Italy
| | - Claudio Gatto
- Research and Development, AL.CHI.MI.A. S.R.L., Viale Austria, 14, 35020 Ponte San Nicolờ, Italy; (U.R.); (C.G.)
| | - Paolo Ruzza
- Institute of Biomolecular Chemistry of CNR (ICB-CNR), Via F. Marzolo, 1, 35131 Padova, Italy;
| | - Jana D’Amato Tóthová
- Research and Development, AL.CHI.MI.A. S.R.L., Viale Austria, 14, 35020 Ponte San Nicolờ, Italy; (U.R.); (C.G.)
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6
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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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7
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Zhou H, Li Y, Yang Y, Liu S, Yang Z. Lanosterol reduces the aggregation propensity of ultraviolet-damaged human γD-crystallins: a molecular dynamics study. Phys Chem Chem Phys 2021; 23:13696-13704. [PMID: 34128026 DOI: 10.1039/d1cp00132a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Ultraviolet (UV) radiation-induced oxidation of tryptophan (Trp) to kynurenine (KN) (TRP > KN) in human γD-crystallins (HγD-Crys) promotes the conversion of proteins into partially unfolded species that act as important precursors for sequential large-scale aggregation. Herein, we report that lanosterol shows protective activity to the structure of the TRP > KN mutant HγD-Crys, particularly its N-terminal domain (N-td), by using all-atom molecular dynamics simulations. The Trp68 > KN mutation significantly destabilizes the originally highly stable "Tyr55-Trp68-Tyr62" cluster, thereby causing loop2, where the mutation occurs, to become very flexible. The large fluctuation of loop2 induces cracks, which appear on the protein surface, resulting in the intrusion of water molecules into the hydrophobic core of the N-td. This event eventually triggers the unfolding of the N-td. However, lanosterol can suppress the large fluctuation of loop2 to protect the structural stability of the mutant N-td, thus reducing the aggregation propensity of the TRP > KN mutant HγD-Crys. This structure protective activity of lanosterol arises from its capability to preferentially bind to the hydrophobic regions near loop2. Thus, lanosterol acts as a "water blocker" to prevent the invasion of solvent molecules into the hydrophobic core. These findings provide some valuable insights into the development of potential lanosterol-based drugs for cataract prevention and treatment.
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Affiliation(s)
- Hong Zhou
- State Key Laboratory of Radiation Medicine and Protection, School for Radiological and Interdisciplinary Sciences (RAD-X), Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou 215123, China.
| | - Youyun Li
- State Key Laboratory of Radiation Medicine and Protection, School for Radiological and Interdisciplinary Sciences (RAD-X), Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou 215123, China.
| | - Ying Yang
- State Key Laboratory of Radiation Medicine and Protection, School for Radiological and Interdisciplinary Sciences (RAD-X), Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou 215123, China.
| | - Shengtang Liu
- State Key Laboratory of Radiation Medicine and Protection, School for Radiological and Interdisciplinary Sciences (RAD-X), Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou 215123, China.
| | - Zaixing Yang
- State Key Laboratory of Radiation Medicine and Protection, School for Radiological and Interdisciplinary Sciences (RAD-X), Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou 215123, China.
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8
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Rana S, Ghosh KS. Inhibition of fibrillation of human γd-crystallin by a flavonoid morin. J Biomol Struct Dyn 2020; 39:4279-4289. [PMID: 32469293 DOI: 10.1080/07391102.2020.1775701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
To inhibit the formation of amyloid fibrils by human γd-crystallin (HGD), a series of four flavonoids (quercertin, rutin, morin and hesperetin) was tested. Only morin had demonstrated significant inhibition of HGD fibrillation. Results from fluorimetric assay techniques (using thioflavin T and ANS), FTIR, circular dichroism and microscopic imaging (fluorescence microscopy and transmission electron microscopy) confirmed HGD fibrillation inhibition by morin. HGD-morin complex formation at ground state resulted tryptophan fluorescence quenching through static mechanism, which was also confirmed by determining the excited-state life time of HGD tryptophan residues. Förster resonance energy transfer occurs from HGD to morin. Synchronous, three-dimensional fluorescence, FTIR and circular dichroism results suggest that major changes in HGD conformation did not occur on binding with morin. The interactions between HGD and morin involve hydrogen bonding and/or van der Waals forces. Docking predictions also support experimental results.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Shiwani Rana
- Department of Chemistry, National Institute of Technology Hamirpur, Hamirpur, Himachal Pradesh, India
| | - Kalyan Sundar Ghosh
- Department of Chemistry, National Institute of Technology Hamirpur, Hamirpur, Himachal Pradesh, India
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9
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Rana S, Sarmah S, Singha Roy A, Ghosh KS. Elucidation of molecular interactions between human γD-crystallin and quercetin, an inhibitor against tryptophan oxidation. J Biomol Struct Dyn 2020; 39:1811-1818. [DOI: 10.1080/07391102.2020.1738960] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Shiwani Rana
- Department of Chemistry, National Institute of Technology Hamirpur, Himachal Pradesh, India
| | - Sharat Sarmah
- Department of Chemistry, National Institute of Technology Meghalaya, Shillong, India
| | - Atanu Singha Roy
- Department of Chemistry, National Institute of Technology Meghalaya, Shillong, India
| | - Kalyan Sundar Ghosh
- Department of Chemistry, National Institute of Technology Hamirpur, Himachal Pradesh, India
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10
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Honisch C, Donadello V, Hussain R, Peterle D, De Filippis V, Arrigoni G, Gatto C, Giurgola L, Siligardi G, Ruzza P. Application of Circular Dichroism and Fluorescence Spectroscopies To Assess Photostability of Water-Soluble Porcine Lens Proteins. ACS OMEGA 2020; 5:4293-4301. [PMID: 32149259 PMCID: PMC7057709 DOI: 10.1021/acsomega.9b04234] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Accepted: 02/04/2020] [Indexed: 06/10/2023]
Abstract
The eye lens is mainly composed of the highly ordered water-soluble (WS) proteins named crystallins. The aggregation and insolubilization of these proteins lead to progressive lens opacification until cataract onset. Although this is a well-known disease, the mechanism of eye lens protein aggregation is not well understood; however, one of the recognized causes of proteins modification is related to the exposure to UV light. For this reason, the spectroscopic properties of WS lens proteins and their stability to UV irradiation have been evaluated by different biophysical methods including synchrotron radiation circular dichroism, fluorescence, and circular dichroism spectroscopies. Moreover, dynamic light scattering, gel electrophoresis, transmission electron microscopy, and protein digestion followed by tandem LC-MS/MS analysis were used to study the morphological and structural changes in protein aggregates induced by exposure to UV light. Our results clearly indicated that the exposure to UV radiation modified the protein conformation, inducing a loss of ordered structure and aggregation. Furthermore, we confirmed that these changes were attributable to the generation of reactive oxygen species due to the irradiation of the protein sample. This approach, involving the photodenaturation of proteins, provides a benchmark in high-throughput screening of small molecules suitable to prevent protein denaturation and aggregation.
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Affiliation(s)
- Claudia Honisch
- Institute
of Biomolecular Chemistry of CNR, Padua
Unit, 35131 Padova, Italy
- Department
of Chemical Sciences, University of Padova, 35131 Padova, Italy
| | - Viola Donadello
- Institute
of Biomolecular Chemistry of CNR, Padua
Unit, 35131 Padova, Italy
| | - Rohanah Hussain
- Diamond
Light Source Ltd., Harwell Science and
Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
| | - Daniele Peterle
- Department
of Pharmaceutical and Pharmacological Sciences, University of Padova, 35131 Padova, Italy
| | - Vincenzo De Filippis
- Department
of Pharmaceutical and Pharmacological Sciences, University of Padova, 35131 Padova, Italy
| | - Giorgio Arrigoni
- Department
of Biomedical Sciences, University of Padova, 35131 Padova, Italy
- Proteomics
Center, University of Padova and Azienda
Ospedaliera di Padova, 35129 Padova, Italy
| | - Claudio Gatto
- Alchilife
Srl, R&D, Viale Austria
14, 35020 Ponte
San Nicolò (PD), Italy
| | - Laura Giurgola
- Alchilife
Srl, R&D, Viale Austria
14, 35020 Ponte
San Nicolò (PD), Italy
| | - Giuliano Siligardi
- Diamond
Light Source Ltd., Harwell Science and
Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
| | - Paolo Ruzza
- Institute
of Biomolecular Chemistry of CNR, Padua
Unit, 35131 Padova, Italy
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11
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Abstract
The crystallins (α, β and γ), major constituent proteins of eye lens fiber cells play their critical role in maintaining the transparency and refractive index of the lens. Under different stress factors and with aging, β- and γ-crystallins start to unfold partially leading to their aggregation. Protein aggregation in lens basically enhances light scattering and causes the vision problem, commonly known as cataract. α-crystallin as a molecular chaperone forms complexes with its substrates (β- and γ-crystallins) to prevent such aggregation. In this chapter, the structural features of β- and γ-crystallins have been discussed. Detailed structural information linked with the high stability of γC-, γD- and γS-crystallins have been incorporated. The nature of homologous and heterologous interactions among crystallins has been deciphered, which are involved in their molecular association and complex formation.
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Affiliation(s)
- Kalyan Sundar Ghosh
- Department of Chemistry, National Institute of Technology Hamirpur, Hamirpur, 177005, Himachal Pradesh, India.
| | - Priyanka Chauhan
- Department of Chemistry, National Institute of Technology Hamirpur, Hamirpur, 177005, Himachal Pradesh, India
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12
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Rana S, Ghosh KS. Protective role of hesperetin against posttranslational oxidation of tryptophan residue of human γD-crystallin: A molecular level study. Arch Biochem Biophys 2019; 679:108204. [PMID: 31758928 DOI: 10.1016/j.abb.2019.108204] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 10/30/2019] [Accepted: 11/19/2019] [Indexed: 11/19/2022]
Abstract
Crystallin proteins undergo various posttranslational modifications with aging of eye lens. Oxidation of tryptophan (Trp) residues of a major γ-crystallin namely human γD-crystallin (HGD) was found to be inhibited by a naturally occurring flavonoid hesperetin at relatively low concentration mostly due to its antioxidant activity. Further the molecular interactions between HGD and hesperetin were elucidated on the basis of the quenching of Trp fluorescence of the protein by the flavonoid. Ground state complexation between HGD and hesperetin caused static quenching of the Trp fluorescence of HGD. Binding and quenching constants were in the order of (103- 104 M-1). Energy transfer from protein to hesperetin was suggested by FRET calculations. Thermodynamic parameters reveal significant hydrophobic association between the protein and hesperetin. Synchronous fluorescence and CD spectroscopic results had ruled out conformational changes in the protein due to binding of hesperetin. Docking studies suggested the proximity of hesperetin with Trp 42, which largely corroborates our experimental findings.
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Affiliation(s)
- Shiwani Rana
- Department of Chemistry, National Institute of Technology Hamirpur, Himachal Pradesh, 177005, India
| | - Kalyan Sundar Ghosh
- Department of Chemistry, National Institute of Technology Hamirpur, Himachal Pradesh, 177005, India.
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13
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Chen JL, Hung CT, Keller JJ, Lin HC, Wu YJ. Proteomic analysis of retinal pigment epithelium cells after exposure to UVA radiation. BMC Ophthalmol 2019; 19:168. [PMID: 31375076 PMCID: PMC6679551 DOI: 10.1186/s12886-019-1151-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2018] [Accepted: 06/24/2019] [Indexed: 01/09/2023] Open
Abstract
Background Age-related macular degeneration (AMD) is the primary cause of blindness and severe vision loss in developed countries and is responsible for 8.7% of blindness globally. Ultraviolet radiation can induce DNA breakdown, produce reactive oxygen species, and has been implicated as a risk factor for AMD. This study investigated the effects of UVA radiation on Human retinal pigment epithelial cell (ARPE-19) growth and protein expression. Methods ARPE-19 cells were irradiated with a UVA lamp at different doses (5, 10, 20, 30 and 40 J/cm2) from 10 cm. Cell viability was determined by MTT assay. Visual inspection was first achieved with inverted light microscopy and then the DeadEnd™ Fluorometric TUNEL System was used to observe nuclear DNA fragmentation. Flow cytometry based-Annexin V-FITC/PI double-staining was used to further quantify cellular viability. Mitochondrial membrane potential was assessed with JC-1 staining. 2D electrophoresis maps of exposed cells were compared to nonexposed cells and gel images analyzed with PDQuest 2-D Analysis Software. Spots with greater than a 1.5-fold difference were selected for LC-MS/MS analysis and some confirmed by western blot. We further investigated whether caspase activation, apoptotic-related mitochondrial proteins, and regulators of ER stress sensors were involved in UVA-induced apoptosis. Results We detected 29 differentially expressed proteins (9 up-regulated and 20 down-regulated) in the exposed cells. Some of these proteins such as CALR, GRP78, NPM, Hsp27, PDI, ATP synthase subunit alpha, PRDX1, and GAPDH are associated with anti-proliferation, induction of apoptosis, and oxidative-stress protection. We also detected altered protein expression levels among caspases (caspase 3 and 9) and in the mitochondrial (cytosolic cytochrome C, AIF, Mcl-1, Bcl-2, Bcl-xl, Bax, Bad, and p-Bad) and ER stress-related (p-PERK, p-eIF2α, ATF4 and CHOP) apoptotic pathways. Conclusions UVA irradiation suppressed the proliferation of ARPE-19 cells in a dose-dependent manner, caused quantitative loses in transmembrane potential (ΔΨm), and induced both early and late apoptosis.
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Affiliation(s)
- Jiunn-Liang Chen
- Department of Ophthalmology, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan.,School of Medicine, National Yang-Ming University, Taipei, Taiwan.,Department of Optometry, Shu-Zen Junior College of Medicine and Management, Kaohsiung, Taiwan
| | - Chun-Tzu Hung
- Department of Ophthalmology, Yuan's General Hospital, Kaohsiung, Taiwan
| | - Joseph Jordan Keller
- College of Medicine, The Ohio State University, Columbus, OH, USA.,School of Public Health, College of Public Health, Taipei Medical University, Taipei, Taiwan.,International Master's Program, College of Health Technology, National Taipei University of Nursing and Health Sciences, Taipei, Taiwan
| | - Hsien-Chung Lin
- Department of Ophthalmology, Yuan's General Hospital, Kaohsiung, Taiwan. .,Department of Ophthalmology, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
| | - Yu-Jen Wu
- Department of Beauty Science, Meiho University, Pingtung, Taiwan.
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14
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Phototoxicity of environmental radiations in human lens: revisiting the pathogenesis of UV-induced cataract. Graefes Arch Clin Exp Ophthalmol 2019; 257:2065-2077. [PMID: 31227898 DOI: 10.1007/s00417-019-04390-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Revised: 05/30/2019] [Accepted: 06/05/2019] [Indexed: 12/13/2022] Open
Abstract
The magnitude of cataract pathology is indeed significant as it is the principal cause of blindness worldwide. Also, the prominence of this concept escalates with the current aging population. The burden of the disease is more tangible in developing countries than developed ones. Regarding this concern, there is a gap in classifying the pathogenesis of the ultraviolet (UV) radiation-induced cataracts and explaining the possible cellular and subcellular pathways. In this review, we aim to revisit the effect of UV radiation on cataracts categorizing the cellular pathways involved. This may help for better pharmaceutical treatment alternatives and their wide-reaching availability. Also, in the last section, we provide an overview of the protecting agents utilized as UV shields. Further studies are required to enlighten new treatment modalities for UV radiation-induced pathologies in human lens.
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15
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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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16
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Zhou H, Liu S, Yin X, Li Z, Yang Z, Zhou R. Molecular Origin of the Stability Difference in Four Shark IgNAR Constant Domains. Biophys J 2019; 116:1907-1917. [PMID: 31060814 DOI: 10.1016/j.bpj.2019.04.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Revised: 02/09/2019] [Accepted: 04/15/2019] [Indexed: 12/11/2022] Open
Abstract
Improving the stability of antibodies for manufacture and shelf life is one of the main focuses of antibody engineering. One stabilization strategy is to perform specific mutations in human antibodies based on highly stable antibodies in other species. To identify the key residues for mutagenesis, it is necessary to understand the roles of these residues in stabilizing the antibody. Here, we use molecular dynamics simulations to study the molecular origin of the four shark immunoglobulin new antigen receptors constant domains (C1-C4). According to the unfolding pathways and the conformational free energy surfaces in 8 M urea at 380 K, the C2 domain is the most stable, followed by C4, C1, and C3, which agrees with the experimental findings. The C1 and C3 domains follow a common unfolding pathway in which the unfolding starts from the edge strands, particularly strand g, and then gradually progresses to the inner strands. Detailed structural analysis of the C2 domain reveals a "sandwich-like" R339-E322-R341 salt-bridge cluster on strand g, which grants ultrahigh stability to the C2 domain. We further design two sets of mutations by mutating E322 to alanine or setting all atomic charges in E322 to zero to break the salt-bridge cluster in the C2 domain, which confirms the importance of the salt bridges in stability. In the C4 domain, the D80-K104 salt bridge on strand g also strengthens the stability. On the other hand, in the C1 and C3 domains, there is no salt bridge on strand g. In addition to the salt bridges, the overall hydrophobicity score of the hydrophobic core is also positively correlated with the domain stability. Our findings provide a detailed microscopic picture of the molecular origin of the four shark immunoglobulin new antigen receptors constant domains that not only explains the differences in their structural stability but also provides important insights into future antibody design.
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Affiliation(s)
- Hong Zhou
- Institute of Quantitative Biology and Medicine, State Key Laboratory of Radiation Medicine and Protection, School of Radiation Medicine and Protection, Collaborative Innovation Center of Radiological Medicine of Jiangsu Higher Education Institutions, Soochow University, Jiangsu, China
| | - Shengtang Liu
- Institute of Quantitative Biology and Medicine, State Key Laboratory of Radiation Medicine and Protection, School of Radiation Medicine and Protection, Collaborative Innovation Center of Radiological Medicine of Jiangsu Higher Education Institutions, Soochow University, Jiangsu, China
| | - Xiuhua Yin
- Institute of Quantitative Biology and Medicine, State Key Laboratory of Radiation Medicine and Protection, School of Radiation Medicine and Protection, Collaborative Innovation Center of Radiological Medicine of Jiangsu Higher Education Institutions, Soochow University, Jiangsu, China
| | - Zengpeng Li
- State Key Laboratory Breeding Base of Marine Genetic Resources, Key Laboratory of Marine Genetic Resources, Fujian Key Laboratory of Marine Genetic Resources, Third Institute of Oceanography, State Oceanic Administration, Xiamen, Fujian, China
| | - Zaixing Yang
- Institute of Quantitative Biology and Medicine, State Key Laboratory of Radiation Medicine and Protection, School of Radiation Medicine and Protection, Collaborative Innovation Center of Radiological Medicine of Jiangsu Higher Education Institutions, Soochow University, Jiangsu, China.
| | - Ruhong Zhou
- Institute of Quantitative Biology and Medicine, State Key Laboratory of Radiation Medicine and Protection, School of Radiation Medicine and Protection, Collaborative Innovation Center of Radiological Medicine of Jiangsu Higher Education Institutions, Soochow University, Jiangsu, China; IBM Thomas J. Watson Research Center, Yorktown Heights, New York; Department of Chemistry, Columbia University, New York, New York.
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17
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Chakraborty A, Nandi SK, Panda AK, Mahapatra PP, Giri S, Biswas A. Probing the structure-function relationship of Mycobacterium leprae HSP18 under different UV radiations. Int J Biol Macromol 2018; 119:604-616. [DOI: 10.1016/j.ijbiomac.2018.07.151] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Revised: 07/01/2018] [Accepted: 07/23/2018] [Indexed: 02/03/2023]
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18
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Ramkumar S, Fan X, Wang B, Yang S, Monnier VM. Reactive cysteine residues in the oxidative dimerization and Cu 2+ induced aggregation of human γD-crystallin: Implications for age-related cataract. Biochim Biophys Acta Mol Basis Dis 2018; 1864:3595-3604. [PMID: 30251679 DOI: 10.1016/j.bbadis.2018.08.021] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2018] [Revised: 07/14/2018] [Accepted: 08/17/2018] [Indexed: 12/15/2022]
Abstract
Cysteine (Cys) residues are major causes of crystallin disulfide formation and aggregation in aging and cataractous human lenses. We recently found that disulfide linkages are highly and partly conserved in β- and γ-crystallins, respectively, in human age-related nuclear cataract and glutathione depleted LEGSKO mouse lenses, and could be mimicked by in vitro oxidation. Here we determined which Cys residues are involved in disulfide-mediated crosslinking of recombinant human γD-crystallin (hγD). In vitro diamide oxidation revealed dimer formation by SDS-PAGE and LC-MS analysis with Cys 111-111 and C111-C19 as intermolecular disulfides and Cys 111-109 as intramolecular sites. Mutation of Cys111 to alanine completely abolished dimerization. Addition of αB-crystallin was unable to protect Cys 111 from dimerization. However, Cu2+-induced hγD-crystallin aggregation was suppressed up to 50% and 80% by mutants C109A and C111A, respectively, as well as by total glutathionylation. In contrast to our recently published results using ICAT-labeling method, manual mining of the same database confirmed the specific involvement of Cys111 in disulfides with no free Cys111 detectable in γD-crystallin from old and cataractous human lenses. Surface accessibility studies show that Cys111 in hγD is the most exposed Cys residue (29%), explaining thereby its high propensity toward oxidation and polymerization in the aging lens.
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Affiliation(s)
| | - Xingjun Fan
- Department of Pathology, Case Western Reserve University, Cleveland, OH 44106, USA.
| | - Benlian Wang
- Center for Proteomics and Bioinformatics, Case Western Reserve University, Cleveland, OH 44106, USA; Department of Nutrition, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Sichun Yang
- Department of Nutrition, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Vincent M Monnier
- Department of Pathology, Case Western Reserve University, Cleveland, OH 44106, USA; Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106, USA.
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19
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Kang H, Yang Z, Zhou R. Lanosterol Disrupts Aggregation of Human γD-Crystallin by Binding to the Hydrophobic Dimerization Interface. J Am Chem Soc 2018; 140:8479-8486. [DOI: 10.1021/jacs.8b03065] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Hongsuk Kang
- Institute of Quantitative Biology, Department of Physics, Zhejiang University, Hangzhou 310027, China
- Computational Biology Center, IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598, United States
| | - Zaixing Yang
- State Key Laboratory of Radiation Medicine and Protection, School for Radiological and Interdisciplinary Sciences (RAD-X) and Collaborative Innovation Centre of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou 215123, China
| | - Ruhong Zhou
- Institute of Quantitative Biology, Department of Physics, Zhejiang University, Hangzhou 310027, China
- Computational Biology Center, IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598, United States
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20
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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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21
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Kang H, Vázquez FX, Zhang L, Das P, Toledo-Sherman L, Luan B, Levitt M, Zhou R. Emerging β-Sheet Rich Conformations in Supercompact Huntingtin Exon-1 Mutant Structures. J Am Chem Soc 2017; 139:8820-8827. [PMID: 28609090 PMCID: PMC5835228 DOI: 10.1021/jacs.7b00838] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
There exists strong correlation between the extended polyglutamines (polyQ) within exon-1 of Huntingtin protein (Htt) and age onset of Huntington's disease (HD); however, the underlying molecular mechanism is still poorly understood. Here we apply extensive molecular dynamics simulations to study the folding of Htt-exon-1 across five different polyQ-lengths. We find an increase in secondary structure motifs at longer Q-lengths, including β-sheet content that seems to contribute to the formation of increasingly compact structures. More strikingly, these longer Q-lengths adopt supercompact structures as evidenced by a surprisingly small power-law scaling exponent (0.22) between the radius-of-gyration and Q-length that is substantially below expected values for compact globule structures (∼0.33) and unstructured proteins (∼0.50). Hydrogen bond analyses further revealed that the supercompact behavior of polyQ is mainly due to the "glue-like" behavior of glutamine's side chains with significantly more side chain-side chain H-bonds than regular proteins in the Protein Data Bank (PDB). The orientation of the glutamine side chains also tend to be "buried" inside, explaining why polyQ domains are insoluble on their own.
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Affiliation(s)
- Hongsuk Kang
- Computational Biology Center, IBM Thomas J. Watson Research Center , Yorktown Heights, New York 10598, United States
| | - Francisco X Vázquez
- Computational Biology Center, IBM Thomas J. Watson Research Center , Yorktown Heights, New York 10598, United States
| | - Leili Zhang
- Computational Biology Center, IBM Thomas J. Watson Research Center , Yorktown Heights, New York 10598, United States
| | - Payel Das
- Computational Biology Center, IBM Thomas J. Watson Research Center , Yorktown Heights, New York 10598, United States
| | | | - Binquan Luan
- Computational Biology Center, IBM Thomas J. Watson Research Center , Yorktown Heights, New York 10598, United States
| | - Michael Levitt
- Department of Structural Biology, Stanford University School of Medicine , Stanford, California 94305, United States
| | - Ruhong Zhou
- Computational Biology Center, IBM Thomas J. Watson Research Center , Yorktown Heights, New York 10598, United States
- Department of Chemistry, Columbia University , New York, New York 10027, United States
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22
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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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23
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Zhang TO, Alperstein AM, Zanni MT. Amyloid β-Sheet Secondary Structure Identified in UV-Induced Cataracts of Porcine Lenses using 2D IR Spectroscopy. J Mol Biol 2017; 429:1705-1721. [PMID: 28454743 PMCID: PMC5493149 DOI: 10.1016/j.jmb.2017.04.014] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Revised: 04/08/2017] [Accepted: 04/24/2017] [Indexed: 02/04/2023]
Abstract
Cataracts are formed by the aggregation of crystallin proteins in the eye lens. Many in vitro studies have established that crystallin proteins precipitate into aggregates that contain amyloid fibers when denatured, but there is little evidence that ex vivo cataracts contain amyloid. In this study, we collect two-dimensional infrared (2D IR) spectra on tissue slices of porcine eye lenses. As shown in control experiments on in vitro αB- and γD-crystallin, 2D IR spectroscopy can identify the highly ordered β-sheets typical of amyloid secondary structure even if the fibers themselves are too short to be resolved with TEM. In ex vivo experiments of acid-treated tissues, characteristic 2D IR features are observed and fibers >50nm in length are resolved by transmission electron microscopy (TEM), consistent with amyloid fibers. In UV-irradiated lens tissues, fibers are not observed with TEM, but highly ordered β-sheets of amyloid secondary structure is identified from the 2D IR spectra. The characteristic 2D IR features of amyloid β-sheet secondary structure are created by as few as four or five strands and so identify amyloid secondary structure even if the aggregates themselves are too small to be resolved with TEM. We discuss these findings in the context of the chaperone system of the lens, which we hypothesize sequesters small aggregates, thereby preventing long fibers from forming. This study expands the scope of heterodyned 2D IR spectroscopy to tissues. The results provide a link between in vitro and ex vivo studies and support the hypothesis that cataracts are an amyloid disease.
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Affiliation(s)
- Tianqi O Zhang
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA.
| | - Ariel M Alperstein
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA.
| | - Martin T Zanni
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA.
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24
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Cetinel S, Semenchenko V, Cho JY, Sharaf MG, Damji KF, Unsworth LD, Montemagno C. UV-B induced fibrillization of crystallin protein mixtures. PLoS One 2017; 12:e0177991. [PMID: 28542382 PMCID: PMC5444657 DOI: 10.1371/journal.pone.0177991] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Accepted: 05/05/2017] [Indexed: 12/28/2022] Open
Abstract
Environmental factors, mainly oxidative stress and exposure to sunlight, induce the oxidation, cross-linking, cleavage, and deamination of crystallin proteins, resulting in their aggregation and, ultimately, cataract formation. Various denaturants have been used to initiate the aggregation of crystallin proteins in vitro. All of these regimens, however, are obviously far from replicating conditions that exist in vivo that lead to cataract formation. In fact, it is our supposition that only UV-B radiation may mimic the observed in vivo cause of crystallin alteration leading to cataract formation. This means of inducing cataract formation may provide the most appropriate in vitro platform for in-depth study of the fundamental cataractous fibril properties and allow for testing of possible treatment strategies. Herein, we showed that cataractous fibrils can be formed using UV-B radiation from α:β:γ crystallin protein mixtures. Characterization of the properties of formed aggregates confirmed the development of amyloid-like fibrils, which are in cross-β-pattern and possibly in anti-parallel β-sheet arrangement. Furthermore, we were also able to confirm that the presence of the molecular chaperone, α-crystallin, was able to inhibit fibril formation, as observed for ‘naturally’ occurring fibrils. Finally, the time-dependent fibrillation profile was found to be similar to the gradual formation of age-related nuclear cataracts. This data provided evidence for the initiation of fibril formation from physiologically relevant crystallin mixtures using UV-B radiation, and that the formed fibrils had several traits similar to that expected from cataracts developing in vivo.
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Affiliation(s)
- Sibel Cetinel
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB, Canada
- Ingenuity Lab., University of Alberta, Edmonton, AB, Canada
| | - Valentyna Semenchenko
- National Institute of Nanotechnology (NINT), 11421, Saskatchewan Drive NW, Edmonton, AB, Canada
| | - Jae-Young Cho
- National Institute of Nanotechnology (NINT), 11421, Saskatchewan Drive NW, Edmonton, AB, Canada
| | - Mehdi Ghaffari Sharaf
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB, Canada
- Ingenuity Lab., University of Alberta, Edmonton, AB, Canada
| | - Karim F. Damji
- Department of Ophthalmology and Visual Sciences, University of Alberta, Edmonton, AB, Canada
| | - Larry D. Unsworth
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB, Canada
- National Institute of Nanotechnology (NINT), 11421, Saskatchewan Drive NW, Edmonton, AB, Canada
- * E-mail: (CM); (LDU)
| | - Carlo Montemagno
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB, Canada
- Ingenuity Lab., University of Alberta, Edmonton, AB, Canada
- * E-mail: (CM); (LDU)
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25
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Chaudhury S, Roy P, Dasgupta S. Green tea flavanols protect human γB-crystallin from oxidative photodamage. Biochimie 2017; 137:46-55. [PMID: 28285129 DOI: 10.1016/j.biochi.2017.02.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Revised: 01/18/2017] [Accepted: 02/27/2017] [Indexed: 12/28/2022]
Abstract
Age related cataract is a major cause of visual loss worldwide that is a result of opacification of the eye lens proteins. One of the major reasons behind this deterioration is UV induced oxidative damage. The study reported here is focused on an investigation of the oxidative stress induced damage to γB-crystallin under UV exposure. Human γB-crystallin has been expressed and purified from E. coli. We have found that epicatechin gallate (ECG) has a higher affinity towards the protein compared to epigallocatechin (EGC). The in vitro study of UV irradiation under oxidative damage to the protein in the presence of increasing concentrations of GTPs is indicative of their effective role as potent inhibitors of oxidative damage. Docking analyses show that the GTPs bind to the cleft between the domains of human γB-crystallin that may be associated with the protection of the protein from oxidative damage.
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Affiliation(s)
| | - Pritam Roy
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
| | - Swagata Dasgupta
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur 721302, India.
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26
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Serebryany E, Takata T, Erickson E, Schafheimer N, Wang Y, King JA. Aggregation of Trp > Glu point mutants of human gamma-D crystallin provides a model for hereditary or UV-induced cataract. Protein Sci 2016; 25:1115-28. [PMID: 26991007 DOI: 10.1002/pro.2924] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Revised: 03/09/2016] [Accepted: 03/10/2016] [Indexed: 12/21/2022]
Abstract
Numerous mutations and covalent modifications of the highly abundant, long-lived crystallins of the eye lens cause their aggregation leading to progressive opacification of the lens, cataract. The nature and biochemical mechanisms of the aggregation process are poorly understood, as neither amyloid nor native-state polymers are commonly found in opaque lenses. The βγ-crystallin fold contains four highly conserved buried tryptophans, which can be oxidized to more hydrophilic products, such as kynurenine, upon UV-B irradiation. We mimicked this class of oxidative damage using Trp→Glu point mutants of human γD-crystallin. Such substitutions may represent a model of UV-induced photodamage-introduction of a charged group into the hydrophobic core generating "denaturation from within." The effects of Trp→Glu substitutions were highly position dependent. While each was destabilizing, only the two located in the bottom of the double Greek key fold-W42E and W130E-yielded robust aggregation of partially unfolded intermediates at 37°C and pH 7. The αB-crystallin chaperone suppressed aggregation of W130E, but not W42E, indicating distinct aggregation pathways from damage in the N-terminal vs C-terminal domain. The W130E aggregates had loosely fibrillar morphology, yet were nonamyloid, noncovalent, showed little surface hydrophobicity, and formed at least 20°C below the melting temperature of the native β-sheets. These features are most consistent with domain-swapped polymerization. Aggregation of partially destabilized crystallins under physiological conditions, as occurs in this class of point mutants, could provide a simple in vitro model system for drug discovery and optimization.
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Affiliation(s)
- Eugene Serebryany
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139
| | - Takumi Takata
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139
| | - Erika Erickson
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139
| | - Nathaniel Schafheimer
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139
| | - Yongting Wang
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139
| | - Jonathan A King
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139
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27
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Xi YB, Chen XJ, Zhao WJ, Yan YB. Congenital Cataract-Causing Mutation G129C in γC-Crystallin Promotes the Accumulation of Two Distinct Unfolding Intermediates That Form Highly Toxic Aggregates. J Mol Biol 2015; 427:2765-81. [DOI: 10.1016/j.jmb.2015.07.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Revised: 06/18/2015] [Accepted: 07/01/2015] [Indexed: 10/23/2022]
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28
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Roy S, Banerjee V, Das KP. Understanding the Physical and Molecular Basis of Stability of Arabidopsis DNA Pol λ under UV-B and High NaCl Stress. PLoS One 2015; 10:e0133843. [PMID: 26230318 PMCID: PMC4521722 DOI: 10.1371/journal.pone.0133843] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Accepted: 07/02/2015] [Indexed: 01/27/2023] Open
Abstract
Here, we have investigated the physical and molecular basis of stability of Arabidopsis DNA Pol λ, the sole X family DNA polymerase member in plant genome, under UV-B and salinity stress in connection with the function of the N-terminal BRCT (breast cancer-associated C terminus) domain and Ser-Pro rich region in the regulation of the overall structure of this protein. Tryptophan fluorescence studies, fluorescence quenching and Bis-ANS binding experiments using purified recombinant full length Pol λ and its N-terminal deletion forms have revealed UV-B induced conformational change in BRCT domain deficient Pol λ. On the other hand, the highly conserved C-terminal catalytic core PolX domain maintained its tertiary folds under similar condition. Circular dichroism (CD) and fourier transform infrared (FT-IR) spectral studies have indicated appreciable change in the secondary structural elements in UV-B exposed BRCT domain deficient Pol λ. Increased thermodynamic stability of the C-terminal catalytic core domain suggested destabilizing effect of the N-terminal Ser-Pro rich region on the protein structure. Urea-induced equilibrium unfolding studies have revealed increased stability of Pol λ and its N-terminal deletion mutants at high NaCl concentration. In vivo aggregation studies using transient expression systems in Arabidopsis and tobacco indicated possible aggregation of Pol λ lacking the BRCT domain. Immunoprecipitation assays revealed interaction of Pol λ with the eukaryotic molecular chaperone HSP90, suggesting the possibility of regulation of Pol λ stability by HSP90 in plant cell. Overall, our results have provided one of the first comprehensive information on the biophysical characteristics of Pol λ and indicated the importance of both BRCT and Ser-Pro rich modules in regulating the stability of this protein under genotoxic stress in plants.
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Affiliation(s)
- Sujit Roy
- Protein Chemistry laboratory, Department of Chemistry, Bose Institute, Kolkata, West Bengal, India
- * E-mail:
| | - Victor Banerjee
- Protein Chemistry laboratory, Department of Chemistry, Bose Institute, Kolkata, West Bengal, India
| | - Kali Pada Das
- Protein Chemistry laboratory, Department of Chemistry, Bose Institute, Kolkata, West Bengal, India
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Kraljević Pavelić S, Klobučar M, Sedić M, Micek V, Gehrig P, Grossman J, Pavelić K, Vojniković B. UV-induced retinal proteome changes in the rat model of age-related macular degeneration. Biochim Biophys Acta Mol Basis Dis 2015; 1852:1833-45. [PMID: 26071645 DOI: 10.1016/j.bbadis.2015.06.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Revised: 05/29/2015] [Accepted: 06/08/2015] [Indexed: 12/23/2022]
Abstract
Age-related macular degeneration (AMD) is characterized by irreversible damage of photoreceptors in the central posterior part of the retina, called the macula and is the most common cause of vision loss in those aged over 50. A growing body of evidence shows that cumulative long-term exposure to UV radiation may be harmful to the retina and possibly leads to AMD irrespective of age. In spite of many research efforts, cellular and molecular mechanisms leading to UV-induced retinal damage and possibly retinal diseases such as AMD are not completely understood. In the present study we explored damage mechanisms accounting for UV-induced retinal phototoxicity in the rats exposed to UVA and UVB irradiation using a proteomics approach. Our study showed that UV irradiation induces profound changes in the retinal proteomes of the rats associated with the disruption of energy homeostasis, oxidative stress, DNA damage response and structural and functional impairments of the interphotoreceptor matrix components and their cell surface receptors such as galectins. Two small leucine-rich proteoglycans, biglycan and lumican, were identified as phototoxicity biomarkers associated with UV-induced disruption of interphotoreceptor matrix (IPM). In addition, UVB induced activation of Src kinase, which could account for cytoskeletal rearrangements in the retina was observed at the proteomics level. Pharmacological intervention either to target Src kinase with the aim of preventing cytoskeletal rearrangements in the retinal pigment epithelium (RPE) and neuronal retina or to help rebuild damaged IPM may provide fresh avenues of treatment for patients suffering from AMD.
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Affiliation(s)
- Sandra Kraljević Pavelić
- University of Rijeka, Department of Biotechnology, Radmile Matejčić 2, HR-51000 Rijeka, Croatia; University of Rijeka, Centre for high-throughput technologies, Radmile Matejčić 2, HR-51000 Rijeka, Croatia.
| | - Marko Klobučar
- University of Rijeka, Department of Biotechnology, Radmile Matejčić 2, HR-51000 Rijeka, Croatia; University of Rijeka, Centre for high-throughput technologies, Radmile Matejčić 2, HR-51000 Rijeka, Croatia
| | - Mirela Sedić
- University of Rijeka, Department of Biotechnology, Radmile Matejčić 2, HR-51000 Rijeka, Croatia; University of Rijeka, Centre for high-throughput technologies, Radmile Matejčić 2, HR-51000 Rijeka, Croatia
| | - Vedran Micek
- The Institute for Medical Research and Occupational Health, Ksaverska cesta 2, POB 291, HR-10001 Zagreb, Croatia
| | - Peter Gehrig
- Functional Genomics Center Zürich, University of Zurich/ETH Zurich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - Jonas Grossman
- Functional Genomics Center Zürich, University of Zurich/ETH Zurich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - Krešimir Pavelić
- University of Rijeka, Department of Biotechnology, Radmile Matejčić 2, HR-51000 Rijeka, Croatia; University of Rijeka, Centre for high-throughput technologies, Radmile Matejčić 2, HR-51000 Rijeka, Croatia
| | - Božidar Vojniković
- University of Applied Sciences Velika Gorica, Zagrebačka cesta 5, Velika Gorica 10410, Croatia
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Abstract
Cataract produces vision loss due to opacification of the lens. Two possible reasons for cataract formation are insolubility of crystallin proteins and fibril (aggregate) formation. Currently, the only available treatment is surgical replacement of the lens with a synthetic one. An alternative treatment that is both economically and technologically accessible is needed in developing countries where untreated cataract and coincident blindness is high, access to trained surgeons is limited, and the cost of surgery may be prohibitive. We present current progress toward the development of a nonsurgical treatment strategy focusing on promoting protein solubility and/or dissolving fibrillar aggregates.
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Serebryany E, King JA. Wild-type human γD-crystallin promotes aggregation of its oxidation-mimicking, misfolding-prone W42Q mutant. J Biol Chem 2015; 290:11491-503. [PMID: 25787081 DOI: 10.1074/jbc.m114.621581] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Indexed: 11/06/2022] Open
Abstract
Non-native protein conformers generated by mutation or chemical damage template aggregation of wild-type, undamaged polypeptides in diseases ranging from amyotrophic lateral sclerosis to cancer. We tested for such interactions in the natively monomeric human eye lens protein γd-crystallin, whose aggregation leads to cataract disease. The oxidation-mimicking W42Q mutant of γd-crystallin formed non-native polymers starting from a native-like state under physiological conditions. Aggregation occurred in the temperature range 35-45 °C, in which the mutant protein began to lose the native conformation of its N-terminal domain. Surprisingly, wild-type γd-crystallin promoted W42Q polymerization in a catalytic manner, even at mutant concentrations too low for homogeneous nucleation to occur. The presence of wild-type protein also downshifted the temperature range of W42Q aggregation. W42Q aggregation required formation of a non-native intramolecular disulfide bond but not intermolecular cross-linking. Transient WT/W42Q binding may catalyze this oxidative misfolding event in the mutant. That a more stable variant in a mixture can specifically promote aggregation of a less stable one rationalizes how extensive aggregation of rare damaged polypeptides can occur during the course of aging.
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Affiliation(s)
- Eugene Serebryany
- From the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Jonathan A King
- From the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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Borzova VA, Markossian KA, Muranov KO, Polyansky NB, Kleymenov SY, Kurganov BI. Quantification of anti-aggregation activity of UV-irradiated α-crystallin. Int J Biol Macromol 2015; 73:84-91. [DOI: 10.1016/j.ijbiomac.2014.10.060] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2014] [Revised: 10/22/2014] [Accepted: 10/27/2014] [Indexed: 10/24/2022]
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Serebryany E, King JA. The βγ-crystallins: native state stability and pathways to aggregation. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2014; 115:32-41. [PMID: 24835736 DOI: 10.1016/j.pbiomolbio.2014.05.002] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Revised: 04/30/2014] [Accepted: 05/02/2014] [Indexed: 01/26/2023]
Abstract
The βγ-crystallins are among the most stable and long-lived proteins in the human body. With increasing age, however, they transform to high molecular weight light-scattering aggregates, resulting in cataracts. This occurs despite the presence in the lens of high concentrations of the a-crystallin chaperones. Aggregation of crystallins can be induced in vitro by a variety of stresses, including acidic pH, ultraviolet light, oxidative damage, heating or freezing, and specific amino acid substitutions. Accumulating evidence points to the existence of specific biochemical pathways of protein: protein interaction and polymerization. We review the methods used for studying crystallin stability and aggregation and discuss the sometimes counterintuitive relationships between factors that favor native state stability and those that favor non-native aggregation. We discuss the behavior of βγ-crystallins in mixtures and their chaperone ability; the consequences of missense mutations and covalent damage to the side-chains; and the evolutionary strategies that have shaped these proteins. Efforts are ongoing to reveal the nature of cataractous crystallin aggregates and understand the mechanisms of aggregation in the context of key models of protein polymerization: amyloid, native-state, and domain-swapped. Such mechanistic understanding is likely to be of value for the development of therapeutic interventions and draw attention to unanswered questions about the relationship between a protein's native state stability and its transformation to an aggregated state.
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Affiliation(s)
- Eugene Serebryany
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - Jonathan A King
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States.
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Schafheimer N, Wang Z, Schey K, King J. Tyrosine/cysteine cluster sensitizing human γD-crystallin to ultraviolet radiation-induced photoaggregation in vitro. Biochemistry 2014; 53:979-90. [PMID: 24410332 PMCID: PMC3954642 DOI: 10.1021/bi401397g] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
![]()
Ultraviolet
radiation (UVR) exposure is a major risk factor for
age-related cataract, a protein-aggregation disease of the human lens
often involving the major proteins of the lens, the crystallins. γD-Crystallin
(HγD-Crys) is abundant in the nucleus of the human lens, and
its folding and aggregation have been extensively studied. Previous
work showed that HγD-Crys photoaggregates in vitro upon exposure
to UVA/UVB light and that its conserved tryptophans are not required
for aggregation. Surprisingly, the tryptophan residues play a photoprotective
role because of a distinctive energy-transfer mechanism. HγD-Crys
also contains 14 tyrosine residues, 12 of which are organized as six
pairs. We investigated the role of the tyrosines of HγD-Crys
by replacing pairs with alanines and monitoring photoaggregation using
light scattering and SDS-PAGE. Mutating both tyrosines in the Y16/Y28
pair to alanine slowed the formation of light-scattering aggregates.
Further mutant studies implicated Y16 as important for photoaggregation.
Mass spectrometry revealed that C18, in contact with Y16, is heavily
oxidized during UVR exposure. Analysis of multiple mutant proteins
by mass spectrometry suggested that Y16 and C18 likely participate
in the same photochemical process. The data suggest an initial photoaggregation
pathway for HγD-Crys in which excited-state Y16 interacts with
C18, initiating radical polymerization.
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Affiliation(s)
- Nathaniel Schafheimer
- Department of Biology, Massachusetts Institute of Technology , 68-330, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
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Yang Z, Xia Z, Huynh T, King JA, Zhou R. Dissecting the contributions of β-hairpin tyrosine pairs to the folding and stability of long-lived human γD-crystallins. NANOSCALE 2014; 6:1797-807. [PMID: 24352614 PMCID: PMC3976203 DOI: 10.1039/c3nr03782g] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Ultraviolet-radiation-induced damage to and aggregation of human lens crystallin proteins are thought to be a significant pathway to age-related cataract. The aromatic residues within the duplicated Greek key domains of γ- and β-crystallins are the main ultraviolet absorbers and are susceptible to direct and indirect ultraviolet damage. The previous site-directed mutagenesis studies have revealed a striking difference for two highly conserved homologous β-hairpin Tyr pairs, at the N-terminal domain (N-td) and C-terminal domain (C-td), respectively, in their contribution to the overall stability of HγD-Crys, but why they behave so differently still remains a mystery. In this paper, we systematically investigated the underlying molecular mechanism and detailed contributions of these two Tyr pairs with large scale molecular dynamics simulations. A series of different tyrosine-to-alanine pair(s) substitutions were performed in either the N-td, the C-td, or both. Our results suggest that the Y45A/Y50A pair substitution in the N-td mainly affects the stability of the N-td itself, while the Y133A/Y138A pair substitution in the C-td leads to a more cooperative unfolding of both N-td and C-td. The stability of motif 2 in the N-td is mainly determined by the interdomain interface, while motif 1 in the N-td or motifs 3 and 4 in the C-td are mainly stabilized by the intradomain hydrophobic core. The damage to any tyrosine pair(s) can directly introduce some apparent water leakage to the hydrophobic core at the interface, which in turn causes a serious loss in the stability of the N-td. However, for the C-td substitutions, it may further impair the stable "sandwich-like" Y133-R167-Y138 cluster (through cation-π interactions) in the wild-type, thus causing the loop regions near the residue A138 to undergo large fluctuations, which in turn results in the intrusion of water into the hydrophobic core of the C-td and induces the C-td to lose its stability. These findings help resolve the "mystery" on why these two Tyr pairs display such a striking difference in their contributions to the overall protein stability despite their highly homologous nature.
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Affiliation(s)
- Zaixing Yang
- Institute of Quantitative Biology and Medicine, SRMP and RAD-X & Collaborative Innovation Center of Suzhou Nano Science and Technology, Jiangsu Provincial Key Laboratory of Radiation Medicine and Protection, Soochow University, Suzhou 215123, China.
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Moran SD, Zhang TO, Decatur SM, Zanni MT. Amyloid fiber formation in human γD-Crystallin induced by UV-B photodamage. Biochemistry 2013; 52:6169-81. [PMID: 23957864 DOI: 10.1021/bi4008353] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
γD-Crystallin is an abundant structural protein of the lens that is found in native and modified forms in cataractous aggregates. We establish that UV-B irradiation of γD-Crystallin leads to structurally specific modifications and precipitation via two mechanisms: amorphous aggregates and amyloid fibers. UV-B radiation causes cleavage of the backbone, in large measure near the interdomain interface, where side chain oxidations are also concentrated. 2D IR spectroscopy and expressed protein ligation localize fiber formation exclusively to the C-terminal domain of γD-Crystallin. The native β-sandwich domains are not retained upon precipitation by either mechanism. The similarities between the amyloid forming pathways when induced by either UV-B radiation or low pH suggest that the propensity for the C-terminal β-sandwich domain to form amyloid β-sheets determines the misfolding pathway independent of the mechanism of denaturation.
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Affiliation(s)
- Sean D Moran
- Department of Chemistry, University of Wisconsin-Madison , 1101 University Avenue, Madison, WI, United States 53706
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