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Karakosta C, Samiotaki M, Panayotou G, Papaconstantinou DS, Moschos MM. Lens Cytoskeleton: An Update on the Etiopathogenesis of Human Cataracts. Cureus 2024; 16:e56793. [PMID: 38650819 PMCID: PMC11035009 DOI: 10.7759/cureus.56793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/23/2024] [Indexed: 04/25/2024] Open
Abstract
A cataract is a loss of the transparency of a normal crystalline lens. Multiple factors, including age as the major risk factor for cataracts, can disturb the transparency of the crystalline lens due to cumulative damage from environmental insults to proteins, particularly crystallins. Lens proteins do not turnover, and crystallins undergo extensive post-translational modifications (PTMs) with age in order to interact with each other and maintain their soluble basis for lens transparency. These PTMs include truncation, oxidation, deamidation, acetylation, phosphorylation, and glycosylation. Cataract formation, apart from protein PTMs, involves protein crosslinking, protein insolubilization, and aggregation. Oxidation is a key feature in age-related cataract formation. Due to the role of genetic and environmental factors, as well as its variable clinical presentation, we consider cataracts to be a multifactorial disease. The preliminary results of our study indicate that proteins implicated in the pathway of a structural constituent of the eye lens (BFSP1, BFSP2, CRYAA, CRYAB, CRYBA, CRYBB, CRYGC, CRYGD, CRYGS, KRTs, and VIM), together with AQP1 and AQP5, may also be involved in lens aging.
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Affiliation(s)
- Christina Karakosta
- Ophthalmology, National and Kapodistrian University of Athens School of Medicine, Athens, GRC
| | - Martina Samiotaki
- Proteomics, Biomedical Sciences Research Center "Alexander Fleming", Athens, GRC
| | - George Panayotou
- Proteomics, Biomedical Sciences Research Center "Alexander Fleming", Athens, GRC
| | - Dimitrios S Papaconstantinou
- Ophthalmology, Gennimatas Hospital, National and Kapodistrian University of Athens School of Medicine, Athens, GRC
| | - Marilita M Moschos
- 1st Department of Ophthalmology, National and Kapodistrian University of Athens, Athens, GRC
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2
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Morvan M, Mikšík I. The chiral proteomic analysis applied to aging collagens by LC-MS: Amino acid racemization, post-translational modifications, and sequence degradations during the aging process. Anal Chim Acta 2023; 1262:341260. [PMID: 37179063 DOI: 10.1016/j.aca.2023.341260] [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: 03/02/2023] [Revised: 04/14/2023] [Accepted: 04/22/2023] [Indexed: 05/15/2023]
Abstract
Collagen is the most abundant protein in the animal and human bodies, and it is not exempt from this aging phenomenon. Some age-related changes may appear on collagen sequences, such as increased surface hydrophobicity, the appearance of post-translational modifications, and amino acids racemization. This study has shown that the protein hydrolysis under deuterium conditions is privileged to limit the natural racemization during the hydrolysis. Indeed, under the deuterium condition, the homochirality of recent collagens is preserved whose amino acids are found in their L-form. However, in aging collagen, a natural amino acid racemization was observed. These results confirmed that the % d-amino acids are progressive according to age. The collagen sequence is degraded over time, and a fifth of the sequence information is lost during aging. Post-translational modifications (PTMs) in aging collagens can be a hypothesis to explain the modification of the hydrophobicity of the protein with the decrease of hydrophilic groups and the increase of hydrophobic groups. Finally, the exact positions of d-amino acids and PTMs have been correlated and elucidated.
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Affiliation(s)
- Marine Morvan
- Institute of Physiology of the Czech Academy of Sciences, Vídeňská 1083, 142 20, Prague, Czech Republic; Department of Analytical Chemistry, Faculty of Chemical Technology, University of Pardubice, Studentská 573, 532 10, Pardubice, Czech Republic.
| | - Ivan Mikšík
- Department of Analytical Chemistry, Faculty of Chemical Technology, University of Pardubice, Studentská 573, 532 10, Pardubice, Czech Republic
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3
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Abstract
Like many biological compounds, proteins are found primarily in their homochiral form. However, homochirality is not guaranteed throughout life. Determining their chiral proteinogenic sequence is a complex analytical challenge. This is because certain d-amino acids contained in proteins play a role in human health and disease. This is the case, for example, with d-Asp in elastin, β-amyloid and α-crystallin which, respectively, have an action on arteriosclerosis, Alzheimer’s disease and cataracts. Sequence-dependent and sequence-independent are the two strategies for detecting the presence and position of d-amino acids in proteins. These methods rely on enzymatic digestion by a site-specific enzyme and acid hydrolysis in a deuterium or tritium environment to limit the natural racemization of amino acids. In this review, chromatographic and electrophoretic techniques, such as LC, SFC, GC and CE, will be recently developed (2018–2020) for the enantioseparation of amino acids and peptides. For future work, the discovery and development of new chiral stationary phases and derivatization reagents could increase the resolution of chiral separations.
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4
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Racemization in cataractous lens from diabetic and aging individuals: analysis of Asp 58 residue in αA-crystallin. Aging (Albany NY) 2021; 13:15255-15268. [PMID: 34096886 PMCID: PMC8221327 DOI: 10.18632/aging.203086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Accepted: 04/29/2021] [Indexed: 11/25/2022]
Abstract
Cataract is the leading cause of visual impairment globally. Racemization of lens proteins may contribute to cataract formation in aging individuals. As a special type of age-related cataract (ARC), diabetic cataract (DC) is characterized by the early onset of cortical opacification and finally developed into a mixed type of cortical and nuclear opacification. We compared racemization of Asp 58 residue, a hotspot position in αA-crystallin, from the cortex and nucleus of diabetic and age-matched senile cataractous lenses, by identifying L-Asp/L-isoAsp/D-Asp/D-isoAsp by mass spectrometry. Compared to nondiabetic cataractous lenses, DC lenses showed a significantly increased cortex/nucleus ratio of D-Asp 58, which originated primarily from an increased percentage of D-Asp 58 in the lens cortex of DC. Moreover, patients diagnosed with diabetes for over 10 years showed a lower cortex/nucleus ratio of D-isoAsp 58 in the lens compared with those who had a shorter duration of diabetes, which originated mainly from an increased percentage of D-isoAsp 58 in the lens nucleus of DC with increasing time of hyperglycemia. Further analysis confirmed decreased protein solubility in diabetic cataractous lenses. The different racemization pattern in DC may be distinguished from ARC and influence its phenotype over the protracted duration of diabetes.
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5
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Mizuno H, Shindo T, Ito K, Sakane I, Miyazaki Y, Toyo'oka T, Todoroki K. Development of a selective and sensitive analytical method to detect isomerized aspartic acid residues in crystallin using a combination of derivatization and liquid chromatography mass spectrometry. J Chromatogr A 2020; 1623:461134. [PMID: 32345439 DOI: 10.1016/j.chroma.2020.461134] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2019] [Revised: 04/13/2020] [Accepted: 04/14/2020] [Indexed: 11/24/2022]
Abstract
The isomerization of amino acids in peptides and proteins induces structural changes and aggregation. The isomerization rate of aspartic acid (Asp) is high and causes various serious diseases including Alzheimer's disease and cataract. Herein, a method for the comprehensive separation and sensitive detection of isomerized crystallin containing Asp (l-α-Asp, l-β-Asp, d-α-Asp, and d-β-Asp) was developed using chiral derivatization and reversed-phase UHPLC separation. Of three candidate derivatization reagents tested for the separation of peptides containing isomerized aspartic acid, 2,5-dioxopyrrolidin-1-yl-1-(4,6-dimethoxy-1,3,5-triazine-2-yl) pyrrolidine-2-carboxylate (DMT-(R)-Pro-OSu) was the most suitable reagent for separating isomerized peptides and improved the sensitivity of mass spectrometry by 50-fold. This method was applied to analyze heat-denatured crystallin. Asp58 and Asp151 residues in αA-crystallin (AAC) exhibited the highest isomerization rate in heated crystallin. Furthermore, the analysis of α-crystallin extracted from bovine eye lens identified isomerized Asp residues (Asp24/35, Asp58, and Asp151 in AAC and Asp140 in αB-crystallin (ABC)). These results indicate that the newly developed method using chiral derivatization provides selective and sensitive analysis of isomerized Asp sites in α-crystallin protein. This novel method will allow for the identification and quantification of isomerized amino acids in crystallin proteins.
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Affiliation(s)
- Hajime Mizuno
- Laboratory of Analytical and Bio-Analytical Chemistry, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Takuya Shindo
- Laboratory of Analytical and Bio-Analytical Chemistry, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Keisuke Ito
- Laboratory of Food Chemistry, School of Food and Nutritional Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Iwao Sakane
- Central Research Institute, ITO EN, Ltd., 21 Mekami, Makinohara, Shizuoka 421-0516, Japan
| | - Yasuto Miyazaki
- Laboratory of Analytical and Bio-Analytical Chemistry, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Toshimasa Toyo'oka
- Laboratory of Analytical and Bio-Analytical Chemistry, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Kenichiro Todoroki
- Laboratory of Analytical and Bio-Analytical Chemistry, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
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6
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Nakayoshi T, Kato K, Fukuyoshi S, Takahashi H, Takahashi O, Kurimoto E, Oda A. Computational studies on nonenzymatic succinimide-formation mechanisms of the aspartic acid residues catalyzed by two water molecules. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2020; 1868:140459. [PMID: 32474105 DOI: 10.1016/j.bbapap.2020.140459] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 05/10/2020] [Accepted: 05/26/2020] [Indexed: 01/31/2023]
Abstract
In the biological proteins, aspartic acid (Asp) residues are prone to nonenzymatic isomerization via a succinimide (Suc) intermediate. Asp-residue isomerization causes the aggregation and the insolubilization of proteins, and is considered to be involved in various age-related diseases. Although Suc intermediate was considered to be formed by nucleophilic attack of the main-chain amide nitrogen of N-terminal side adjacent residue to the side-chain carboxyl carbon of Asp residue, previous studies have shown that the nucleophilic attack is more likely to proceed via iminol tautomer when the water molecules act as catalysts. However, the full pathway to Suc-intermediate formation has not been investigated, and the experimental analyses for the Asp-residue isomerization mechanism at atomic and molecular levels, such as the analysis of the transition state geometry, are difficult. In the present study, we computationally explored the full pathways for Suc-intermediate formation from Asp residues. The calculations were performed two types of reactant complexes, and all energy minima and TS geometries were optimized using B3LYP density functional methods. As a result, the SI-intermediate formation was divided into three processes, i.e., iminolization, cyclization, and dehydration processes, and the activation energies were calculated to be 26.1 or 28.4 kcal mol-1. These values reproduce the experimental data. The computational results show that abundant water molecules in living organisms are effective catalysts for the Asp-residue isomerization.
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Affiliation(s)
- Tomoki Nakayoshi
- Graduate School of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya, Aichi 468-8503, Japan; Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa 920-1192, Japan.
| | - Koichi Kato
- Graduate School of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya, Aichi 468-8503, Japan; Department of Pharmacy, Kinjo Gakuin University, 2-1723 Omori, Moriyama-ku, Nagoya, Aichi 463-8521, Japan.
| | - Shuichi Fukuyoshi
- Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa 920-1192, Japan.
| | - Hiro Takahashi
- Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa 920-1192, Japan.
| | - Ohgi Takahashi
- Faculty of Pharmaceutical Sciences, Tohoku Medical and Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai, Miyagi 981-8558, Japan.
| | - Eiji Kurimoto
- Graduate School of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya, Aichi 468-8503, Japan.
| | - Akifumi Oda
- Graduate School of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya, Aichi 468-8503, Japan; Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa 920-1192, Japan; Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
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7
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Truscott RJW, Friedrich MG. Molecular Processes Implicated in Human Age-Related Nuclear Cataract. Invest Ophthalmol Vis Sci 2020; 60:5007-5021. [PMID: 31791064 PMCID: PMC7043214 DOI: 10.1167/iovs.19-27535] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Human age-related nuclear cataract is commonly characterized by four biochemical features that involve modifications to the structural proteins that constitute the bulk of the lens: coloration, oxidation, insolubility, and covalent cross-linking. Each of these is progressive and increases as the cataract worsens. Significant progress has been made in understanding the origin of the factors that underpin the loss of lens transparency. Of these four hallmarks of cataract, it is protein-protein cross-linking that has been the most intransigent, and it is only recently, with the advent of proteomic methodology, that mechanisms are being elucidated. A diverse range of cross-linking processes involving several amino acids have been uncovered. Although other hypotheses for the etiology of cataract have been advanced, it is likely that spontaneous decomposition of the structural proteins of the lens, which do not turn over, is responsible for the age-related changes to the properties of the lens and, ultimately, for cataract. Cataract may represent the first and best characterized of a number of human age-related diseases where spontaneous protein modification leads to ongoing deterioration and, ultimately, a loss of tissue function.
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Affiliation(s)
- Roger J W Truscott
- Illawarra Health and Medical Research Institute, University of Wollongong, Australia
| | - Michael G Friedrich
- Illawarra Health and Medical Research Institute, University of Wollongong, Australia
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8
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Schey KL, Wang Z, Friedrich MG, Garland DL, Truscott RJW. Spatiotemporal changes in the human lens proteome: Critical insights into long-lived proteins. Prog Retin Eye Res 2019; 76:100802. [PMID: 31704338 DOI: 10.1016/j.preteyeres.2019.100802] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Revised: 10/24/2019] [Accepted: 10/30/2019] [Indexed: 12/15/2022]
Abstract
The ocular lens is a unique tissue that contains an age gradient of cells and proteins ranging from newly differentiated cells containing newly synthesized proteins to cells and proteins that are as old as the organism. Thus, the ocular lens is an excellent model for studying long-lived proteins (LLPs) and the effects of aging and post-translational modifications on protein structure and function. Given the architecture of the lens, with young fiber cells in the outer cortex and the oldest cells in the lens nucleus, spatially-resolved studies provide information on age-specific protein changes. In this review, experimental strategies and proteomic methods that have been used to examine age-related and cataract-specific changes to the human lens proteome are described. Measured spatio-temporal changes in the human lens proteome are summarized and reveal a highly consistent, time-dependent set of modifications observed in transparent human lenses. Such measurements have led to the discovery of cataract-specific modifications and the realization that many animal systems are unsuitable to study many of these modifications. Mechanisms of protein modifications such as deamidation, racemization, truncation, and protein-protein crosslinking are presented and the implications of such mechanisms for other long-lived proteins in other tissues are discussed in the context of age-related neurological diseases. A comprehensive understanding of LLP modifications will enhance our ability to develop new therapies for the delay, prevention or reversal of age-related diseases.
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Affiliation(s)
- Kevin L Schey
- Department of Biochemistry, Vanderbilt University, USA.
| | - Zhen Wang
- Department of Biochemistry, Vanderbilt University, USA
| | - Michael G Friedrich
- Illawarra Health and Medical Research Institute, University of Wollongong, Australia
| | | | - Roger J W Truscott
- Illawarra Health and Medical Research Institute, University of Wollongong, Australia
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9
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Warmack RA, Shawa H, Liu K, Lopez K, Loo JA, Horwitz J, Clarke SG. The l-isoaspartate modification within protein fragments in the aging lens can promote protein aggregation. J Biol Chem 2019; 294:12203-12219. [PMID: 31239355 DOI: 10.1074/jbc.ra119.009052] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 06/05/2019] [Indexed: 01/15/2023] Open
Abstract
Transparency in the lens is accomplished by the dense packing and short-range order interactions of the crystallin proteins in fiber cells lacking organelles. These features are accompanied by a lack of protein turnover, leaving lens proteins susceptible to a number of damaging modifications and aggregation. The loss of lens transparency is attributed in part to such aggregation during aging. Among the damaging post-translational modifications that accumulate in long-lived proteins, isomerization at aspartate residues has been shown to be extensive throughout the crystallins. In this study of the human lens, we localize the accumulation of l-isoaspartate within water-soluble protein extracts primarily to crystallin peptides in high-molecular weight aggregates and show with MS that these peptides are from a variety of crystallins. To investigate the consequences of aspartate isomerization, we investigated two αA crystallin peptides 52LFRTVLDSGISEVR65 and 89VQDDFVEIH98, identified within this study, with the l-isoaspartate modification introduced at Asp58 and Asp91, respectively. Importantly, whereas both peptides modestly increase protein precipitation, the native 52LFRTVLDSGISEVR65 peptide shows higher aggregation propensity. In contrast, the introduction of l-isoaspartate within a previously identified anti-chaperone peptide from water-insoluble aggregates, αA crystallin 66SDRDKFVIFL(isoAsp)VKHF80, results in enhanced amyloid formation in vitro The modification of this peptide also increases aggregation of the lens chaperone αB crystallin. These findings may represent multiple pathways within the lens wherein the isomerization of aspartate residues in crystallin peptides differentially results in peptides associating with water-soluble or water-insoluble aggregates. Here the eye lens serves as a model for the cleavage and modification of long-lived proteins within other aging tissues.
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Affiliation(s)
- Rebeccah A Warmack
- Department of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095; Molecular Biology Institute, UCLA, Los Angeles, California 90095
| | - Harrison Shawa
- Department of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095; Molecular Biology Institute, UCLA, Los Angeles, California 90095
| | - Kate Liu
- Department of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095; Molecular Biology Institute, UCLA, Los Angeles, California 90095
| | - Katia Lopez
- Department of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095; Molecular Biology Institute, UCLA, Los Angeles, California 90095
| | - Joseph A Loo
- Department of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095; Molecular Biology Institute, UCLA, Los Angeles, California 90095
| | - Joseph Horwitz
- Molecular Biology Institute, UCLA, Los Angeles, California 90095; Jules Stein Eye Institute, UCLA, Los Angeles, California 90095
| | - Steven G Clarke
- Department of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095; Molecular Biology Institute, UCLA, Los Angeles, California 90095.
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10
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Spontaneous cross-linking of proteins at aspartate and asparagine residues is mediated via a succinimide intermediate. Biochem J 2018; 475:3189-3200. [PMID: 30181147 DOI: 10.1042/bcj20180529] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Revised: 08/24/2018] [Accepted: 08/31/2018] [Indexed: 11/17/2022]
Abstract
The breakdown of long-lived proteins (LLPs) is associated with aging, as well as disease; however, our understanding of the molecular processes involved is still limited. Of particular relevance, cross-linked proteins are often reported in aged tissues but the mechanisms for their formation are poorly understood. In the present study, sites of protein cross-linking in human ocular lenses were characterized using proteomic techniques. In long-lived lens proteins, several sites of cross-linking were found to involve the addition of Lys to Asp or Asn residues. Using model peptides containing Asp or Asn, a mechanism was elucidated that involves a succinimide intermediate. Succinimides formed readily from Asn at neutral pH, whereas a higher rate of formation from Asp peptides was observed at more acidic pHs. Succinimides were found to be relatively stable in the absence of nucleophiles. Since racemization of Asp residues, as well as deamidation of Asn, involves a succinimide intermediate, sites of d-Asp and isoAsp in LLPs should also be considered as potential sites of protein covalent cross-linking.
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11
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Can the Fact That Myelin Proteins Are Old and Break down Explain the Origin of Multiple Sclerosis in Some People? J Clin Med 2018; 7:jcm7090281. [PMID: 30223497 PMCID: PMC6162792 DOI: 10.3390/jcm7090281] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Revised: 09/11/2018] [Accepted: 09/12/2018] [Indexed: 01/01/2023] Open
Abstract
Recent discoveries may change the way that multiple sclerosis (MS) is viewed, particularly with regard to the reasons for the untoward immune response. The fact that myelin proteins are long-lived, and that by the time we are adults, they are extensively degraded, alters our perspective on the reasons for the onset of autoimmunity and the origin of MS. For example, myelin basic protein (MBP) from every human brain past the age of 20 years, is so greatly modified, that it is effectively a different protein from the one that was laid down in childhood. Since only a subset of people with such degraded MBP develop MS, a focus on understanding the mechanism of immune responses to central nervous system (CNS) antigens and cerebral immune tolerance appear to be worthwhile avenues to explore. In accord with this, it will be productive to examine why all people, whose brains contain large quantities of a "foreign antigen", do not develop MS. Importantly for the potential causation of MS, MBP from MS patients breaks down differently from the MBP in aged controls. If the novel structures formed in these MS-specific regions are particularly antigenic, it could help explain the origin of MS. If verified, these findings could provide an avenue for the rational synthesis of drugs to prevent and treat MS.
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Abstract
Cataract is a major cause of blindness worldwide. It is characterized by lens opacification and is accompanied by extensive posttranslational modifications (PTMs) in various proteins. PTMs play an essential role in lens opacification. Several PTMs have been described in proteins isolated from relatively old human lenses, including phosphorylation, deamidation, racemization, truncation, acetylation, and methylation. An overwhelming majority of previous cataract proteomic studies have exclusively focused on crystallin proteins, which are the most abundant proteome components of the lens. To investigate the proteome of cataract markers, this chapter focuses on the proteomic research on the functional relevance of the major PTMs in crystallins of human cataractous lenses. Elucidating the role of these modifications in cataract formation has been a challenging task because they are among the most difficult PTMs to study analytically. The proteomic status of some amides presents similar properties in normal aged and cataractous lenses, whereas some may undergo greater PTMs in cataract. Therefore, it is of great importance to review the current proteomic research on crystallins, the major protein markers in different types of cataract, to elucidate the pathogenesis of this major human-blinding condition.
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Affiliation(s)
- Keke Zhang
- Eye Institute, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China; Department of Ophthalmology, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China; Key Laboratory of Myopia, Ministry of Health PR China, Shanghai, China; Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai Medical College, Fudan University, Shanghai, China
| | - Xiangjia Zhu
- Eye Institute, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China; Department of Ophthalmology, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China; Key Laboratory of Myopia, Ministry of Health PR China, Shanghai, China; Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai Medical College, Fudan University, Shanghai, China
| | - Yi Lu
- Eye Institute, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China; Department of Ophthalmology, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China; Key Laboratory of Myopia, Ministry of Health PR China, Shanghai, China; Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai Medical College, Fudan University, Shanghai, China
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13
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Zhu XJ, Zhang KK, He WW, Du Y, Hooi M, Lu Y. Racemization at the Asp 58 residue in αA-crystallin from the lens of high myopic cataract patients. J Cell Mol Med 2017; 22:1118-1126. [PMID: 28994184 PMCID: PMC5783843 DOI: 10.1111/jcmm.13363] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Accepted: 07/19/2017] [Indexed: 01/25/2023] Open
Abstract
Post-translational modifications in lens proteins are key causal factors in cataract. As the most abundant post-translational modification in the lens, racemization may be closely related to the pathogenesis of cataract. Racemization of αA-crystallin, a crucial structural and heat shock protein in the human lens, could significantly influence its structure and function. In previous studies, elevated racemization from l-Asp 58 to d-isoAsp58 in αA-crystallin has been found in age-related cataract (ARC) lenses compared to normal aged human lenses. However, the role of racemization in high myopic cataract (HMC), which is characterized by an early onset of nuclear cataract, remains unknown. In the current study, apparently different from ARC, significantly increased racemization from l-Asp 58 to d-Asp 58 in αA-crystallin was identified in HMC lenses. The average racemization rates for each Asp isoform were calculated in ARC and HMC group. In ARC patients, the conversion of l-Asp 58 to d-isoAsp 58, up to 31.89%, accounted for the main proportion in racemization, which was in accordance with the previous studies. However, in HMC lenses, the conversion of l-Asp 58 to d-Asp 58, as high as 35.44%, accounted for the largest proportion of racemization in αA-crystallin. The different trend in the conversion of αA-crystallin by racemization, especially the elevated level of d-Asp 58 in HMC lenses, might prompt early cataractogenesis and a possible explanation of distinct phenotypes of cataract in HMC.
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Affiliation(s)
- Xiang-Jia Zhu
- Eye Institute, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,Department of Ophthalmology, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,Key Laboratory of Myopia, Ministry of Health PR China, Shanghai, China.,Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai Medical College, Fudan University, Shanghai, China
| | - Ke-Ke Zhang
- Eye Institute, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,Department of Ophthalmology, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,Key Laboratory of Myopia, Ministry of Health PR China, Shanghai, China.,Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai Medical College, Fudan University, Shanghai, China
| | - Wen-Wen He
- Eye Institute, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,Department of Ophthalmology, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,Key Laboratory of Myopia, Ministry of Health PR China, Shanghai, China.,Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai Medical College, Fudan University, Shanghai, China
| | - Yu Du
- Eye Institute, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,Department of Ophthalmology, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,Key Laboratory of Myopia, Ministry of Health PR China, Shanghai, China.,Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai Medical College, Fudan University, Shanghai, China
| | | | - Yi Lu
- Eye Institute, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,Department of Ophthalmology, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,Key Laboratory of Myopia, Ministry of Health PR China, Shanghai, China.,Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai Medical College, Fudan University, Shanghai, China
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14
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Lyon YA, Sabbah GM, Julian RR. Identification of Sequence Similarities among Isomerization Hotspots in Crystallin Proteins. J Proteome Res 2017; 16:1797-1805. [PMID: 28234481 PMCID: PMC5387677 DOI: 10.1021/acs.jproteome.7b00073] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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The eye lens crystallins represent
an ideal target for studying
the effects of aging on protein structure. Herein we examine separately
the water-soluble (WS) and water-insoluble (WI) crystallin fractions
and identify sites of isomerization and epimerization. Both collision-induced
dissociation and radical-directed dissociation are needed for detection
of these non-mass-shifting post-translational modifications. Isomerization
levels differ significantly between the WS and the WI fractions from
sheep, pig, and cow eye lenses. Residues that are most susceptible
to isomerization are identified site-specifically and are found to
reside in structurally disordered regions. However, isomerization
in structured domains, although less common, often yields more dramatic
effects on solubility. Numerous isomerization hotspots were also identified
and occur in regions with aspartic acid and serine repeats. For example, 128KMEIVDDDVPSLW140 in βB3
crystallin contains three sequential aspartic acid residues and is
isomerized heavily in the WI fractions, while it is not modified at
all in the WS fractions. Potential causes for enhanced isomerization
at sites with acidic residue repeats are presented. The importance
of acidic residue repeats extends beyond the lens, as they are found
in many other long-lived proteins associated with disease.
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Affiliation(s)
- Yana A Lyon
- Department of Chemistry, University of California , Riverside, 501 Big Springs Road, Riverside, California 92521, United States
| | - Georgette M Sabbah
- Department of Chemistry, University of California , Riverside, 501 Big Springs Road, Riverside, California 92521, United States
| | - Ryan R Julian
- Department of Chemistry, University of California , Riverside, 501 Big Springs Road, Riverside, California 92521, United States
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15
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Lim JC, Umapathy A, Donaldson PJ. Tools to fight the cataract epidemic: A review of experimental animal models that mimic age related nuclear cataract. Exp Eye Res 2016; 145:432-443. [DOI: 10.1016/j.exer.2015.09.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Revised: 09/07/2015] [Accepted: 09/14/2015] [Indexed: 12/22/2022]
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16
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Biophysical chemistry of the ageing eye lens. Biophys Rev 2015; 7:353-368. [PMID: 28510099 DOI: 10.1007/s12551-015-0176-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Accepted: 06/23/2015] [Indexed: 12/24/2022] Open
Abstract
This review examines both recent and historical literature related to the biophysical chemistry of the proteins in the ageing eye, with a particular focus on cataract development. The lens is a vital component of the eye, acting as an optical focusing device to form clear images on the retina. The lens maintains the necessary high transparency and refractive index by expressing crystallin proteins in high concentration and eliminating all large cellular structures that may cause light scattering. This has the consequence of eliminating lens fibre cell metabolism and results in mature lens fibre cells having no mechanism for protein expression and a complete absence of protein recycling or turnover. As a result, the crystallins are some of the oldest proteins in the human body. Lack of protein repair or recycling means the lens tends to accumulate damage with age in the form of protein post-translational modifications. The crystallins can be subject to a wide range of age-related changes, including isomerisation, deamidation and racemisation. Many of these modification are highly correlated with cataract formation and represent a biochemical mechanism for age-related blindness.
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17
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Fujii N, Takata T, Fujii N, Aki K. Isomerization of aspartyl residues in crystallins and its influence upon cataract. Biochim Biophys Acta Gen Subj 2015; 1860:183-91. [PMID: 26275494 DOI: 10.1016/j.bbagen.2015.08.001] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Revised: 07/25/2015] [Accepted: 08/03/2015] [Indexed: 12/26/2022]
Abstract
BACKGROUND Age-related cataracts, which probably form due to insolubilization of lens proteins, can lead to loss of vision. Although the exact reason is unknown, lens protein aggregation may be triggered by increases in PTMs such as D-β-, L-β- and D-α-Asp isomers. These isomers have been observed in aged lens; however, there have been few quantitative and site-specific studies owing to the lack of a quick and precise method for distinguishing between D- and L-Asp in a peptide or protein. SCOPE OF REVIEW We describe a new method for detecting peptides containing Asp isomers at individual sites in any protein by using an LC-MS/MS system combined with commercial enzymes that specifically react with different isomers. We also summarize current data on the effect of Asp isomerization on lens crystallins. MAJOR CONCLUSIONS The new technique enabled the analysis of isomers of Asp residues in lens proteins precisely and quickly. An extensive proportion of Asp isomerization was observed at all Asp sites of crystallins in the insoluble fraction of aged lens. In addition, d-amino acid substitutions in crystallin-mimic peptides showed altered structural formation and function. These results indicate that isomerization of Asp residues affects the stability, structure and inter-subunit interaction of lens crystallins, which will induce crystallin aggregation and insolubilization, disrupt the associated functions, and ultimately contribute to the onset of senile cataract formation. GENERAL SIGNIFICANCE The mechanism underlying the onset of age-related diseases may involve isomerization, whereby D-amino acids are incorporated in the L-amino acid world of life. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.
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Affiliation(s)
- Noriko Fujii
- Research Reactor Institute, Kyoto University, Kumatori, Osaka 590-0494, Japan.
| | - Takumi Takata
- Research Reactor Institute, Kyoto University, Kumatori, Osaka 590-0494, Japan
| | - Norihiko Fujii
- Radioisotope Research Center, Teikyo University, Kaga Itabashi-ku, Tokyo 173-8605, Japan
| | - Kenzo Aki
- Faculty of Pharmaceutical Sciences, Himeji Dokkyo University, Kamiohno, Himeji 670-8524, Japan
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18
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Zhu XJ, Zhang KK, Zhou P, Jiang CH, Lu Y. αA-crystallin gene CpG islands hypermethylation in nuclear cataract after pars plana vitrectomy. Graefes Arch Clin Exp Ophthalmol 2015; 253:1043-51. [PMID: 25663476 DOI: 10.1007/s00417-015-2949-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Revised: 01/20/2015] [Accepted: 01/22/2015] [Indexed: 12/30/2022] Open
Abstract
PURPOSE To investigate the DNA methylation status of αA-crystallin gene in cataract secondary to pars plana vitrectomy. METHODS Anterior capsular membranes of 40 eyes of 40 patients with cataract secondary to vitrectomy were collected. Another 20 eyes of 20 patients who received pars plana vitrectomy and phacoemulsification in the primary procedure, were recruited as control. Methylation status of the CpG islands of αA-crystallin gene was analyzed by pyrosequencing. Expression of αA-crystallin was evaluated by real-time polymerase chain reaction and western blot. RESULTS In the post vitrectomy group, five patients with posterior subcapsular opacity and four patients with cortical opacity were excluded from further analysis. The remaining 31 patients with nuclear cataract were assigned into two groups according to tamponade types: 19 of octafluoropropane (C3F8) and 12 of silicone oil (SiO). The average nuclear color grading was elevated both in C3F8 and SiO groups after vitrectomy. Compared to the control group, hypermethylation of the CpG islands in the αA-crystallin gene promoter was found in both post vitrectomy groups, accompanied by significantly reduced αA-crystallin expression. No statistically significant differences were found between the C3F8 and SiO groups either for DNA methylation status or αA-crystallin expression. CONCLUSIONS CpG islands hypermethylation of αA-crystallin gene may be involved in nuclear cataract formation after pars plana vitrectomy.
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Affiliation(s)
- Xiang-Jia Zhu
- Department of Ophthalmology, Eye and ENT Hospital, Fudan University, 83 Fenyang Road, Shanghai, 200031, People's Republic of China
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19
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Patananan AN, Capri J, Whitelegge JP, Clarke SG. Non-repair pathways for minimizing protein isoaspartyl damage in the yeast Saccharomyces cerevisiae. J Biol Chem 2014; 289:16936-53. [PMID: 24764295 DOI: 10.1074/jbc.m114.564385] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The spontaneous degradation of asparaginyl and aspartyl residues to isoaspartyl residues is a common type of protein damage in aging organisms. Although the protein-l-isoaspartyl (d-aspartyl) O-methyltransferase (EC 2.1.1.77) can initiate the repair of l-isoaspartyl residues to l-aspartyl residues in most organisms, no gene homolog or enzymatic activity is present in the budding yeast Saccharomyces cerevisiae. Therefore, we used biochemical approaches to elucidate how proteins containing isoaspartyl residues are metabolized in this organism. Surprisingly, the level of isoaspartyl residues in yeast proteins (50-300 pmol of isoaspartyl residues/mg of protein extract) is comparable with organisms with protein-l-isoaspartyl (d-aspartyl) O-methyltransferase, suggesting a novel regulatory pathway. Interfering with common protein quality control mechanisms by mutating and inhibiting the proteasomal and autophagic pathways in vivo did not increase isoaspartyl residue levels compared with wild type or uninhibited cells. However, the inhibition of metalloproteases in in vitro aging experiments by EDTA resulted in an ∼3-fold increase in the level of isoaspartyl-containing peptides. Characterization by mass spectrometry of these peptides identified several proteins involved in metabolism as targets of isoaspartyl damage. Further analysis of these peptides revealed that many have an N-terminal isoaspartyl site and originate from proteins with short half-lives. These results suggest that one or more metalloproteases participate in limiting isoaspartyl formation by robust proteolysis.
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Affiliation(s)
- Alexander N Patananan
- From the Department of Chemistry and Biochemistry and the Molecular Biology Institute and
| | - Joseph Capri
- the Pasarow Mass Spectrometry Laboratory, Neuropsychiatric Institute-Semel Institute for Neuroscience and Human Behavior, UCLA, Los Angeles, California 90095
| | - Julian P Whitelegge
- the Pasarow Mass Spectrometry Laboratory, Neuropsychiatric Institute-Semel Institute for Neuroscience and Human Behavior, UCLA, Los Angeles, California 90095
| | - Steven G Clarke
- From the Department of Chemistry and Biochemistry and the Molecular Biology Institute and
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