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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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2
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Liu XX, Ye H, Wang P, Li LX, Zhang Y, Zhang JY. Proteomic-based identification of HSP70 as a tumor-associated antigen in ovarian cancer. Oncol Rep 2017; 37:2771-2778. [DOI: 10.3892/or.2017.5525] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Accepted: 11/21/2016] [Indexed: 11/06/2022] Open
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3
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Thornell E, Aquilina A. Regulation of αA- and αB-crystallins via phosphorylation in cellular homeostasis. Cell Mol Life Sci 2015; 72:4127-37. [PMID: 26210153 PMCID: PMC11113999 DOI: 10.1007/s00018-015-1996-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Revised: 07/10/2015] [Accepted: 07/16/2015] [Indexed: 11/27/2022]
Abstract
αA-Crystallin (αA) and αB-crystallin (αB) are small heat shock proteins responsible for the maintenance of transparency in the lens. In non-lenticular tissues, αB is involved in both maintenance of the cytoskeleton and suppression of neurodegeneration amongst other roles. Despite their importance in maintaining cellular health, modifications and mutations to αA and αB appear to play a role in disease states such as cataract and myopathies. The list of modifications that have been reported is extensive and include oxidation, disulphide bond formation, C- and N-terminal truncation, acetylation, carboxymethylation, carboxyethylation, carbamylation, deamidation, phosphorylation and methylation. Such modifications, notably phosphorylation, are alleged to cause changes to chaperone activity by inducing substructural changes and altering subunit exchange dynamics. Although the effect modification has on the activities of αA and αB is contentious, it has been proposed that these changes are responsible for the induction of hyperactivity and are thereby indirectly responsible for protein deposition characteristic of many diseases associated with αA and αB. This review compiles all reported sites of αA and αB modifications, and investigates the role phosphorylation, in particular, plays in cellular processes.
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Affiliation(s)
- Erin Thornell
- Illawarra Health and Medical Research Institute, University of Wollongong, Northfields Ave., Wollongong, NSW, 2522, Australia.
| | - Andrew Aquilina
- Illawarra Health and Medical Research Institute, University of Wollongong, Northfields Ave., Wollongong, NSW, 2522, Australia
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4
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Nakajima E, David LL, Riviere MA, Azuma M, Shearer TR. Human and monkey lenses cultured with calcium ionophore form alphaB-crystallin lacking the C-terminal lysine, a prominent feature of some human cataracts. Invest Ophthalmol Vis Sci 2009; 50:5828-36. [PMID: 19608539 DOI: 10.1167/iovs.09-4015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Elevation of lens calcium occurs in both human and experimental animal cataracts, and opacification may result from calcium-activated proteolysis. The purpose of the present study was to determine whether calcium accumulation in cultured human and Macaca mulatta lenses results in proteolysis of crystallins, the major lens proteins. METHODS Two-dimensional electrophoresis and mass spectrometry were used to construct detailed maps of human and monkey lens crystallins so that proteolysis after calcium accumulation could be monitored and the altered crystallins identified. Human and macaque lenses cultured in A23187 showed elevated lenticular calcium and superficial cortical opacities. The carboxypeptidase E (CPE) gene is expressed in human lens, and its presence in lens fibers was demonstrated by Western blot. To investigate whether CPE could cause similar truncation, purified alphaB-crystallin and CPE were incubated in vitro. RESULTS The major change observed in the crystallins of these cultured lenses was the accumulation of alphaB(1-174)-crystallin resulting from the loss of a C-terminal lysine. This result was significant, because similar appearance of alphaB(1-174) is a prominent change in some human cataracts. alphaB-crystallin and CPE incubation result in the formation of alphaB(1-174)-crystallin. This truncation was specific to alphaB(1-174)-crystallin, since other crystallins were not proteolyzed. Although a weaker activator than zinc, calcium activated CPE in vitro. CONCLUSIONS Since zinc concentrations did not increase during culture in A23187, calcium uptake in the lens may be responsible for CPE activation and alphaB(1-174) formation during cataract.
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Affiliation(s)
- Emi Nakajima
- Laboratory of Ocular Sciences, Senju Pharmaceutical Corporation Limited, Beaverton, Oregon 97006, USA.
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5
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Hayes VH, Devlin G, Quinlan RA. Truncation of alphaB-crystallin by the myopathy-causing Q151X mutation significantly destabilizes the protein leading to aggregate formation in transfected cells. J Biol Chem 2008; 283:10500-12. [PMID: 18230612 DOI: 10.1074/jbc.m706453200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Here we investigate the effects of a myopathy-causing mutation in alphaB-crystallin, Q151X, upon its structure and function. This mutation removes the C-terminal domain of alphaB-crystallin, which is expected to compromise both its oligomerization and chaperone activity. We compared this to two other alphaB-crystallin mutants (450delA, 464delCT) and also to a series of C-terminal truncations (E164X, E165X, K174X, and A171X). We find that the effects of the Q151X mutation were not always as predicted. Specifically, we have found that although the Q151X mutation decreased oligomerization of alphaB-crystallin and even increased some chaperone activities, it also significantly destabilized alphaB-crystallin causing it to self-aggregate. This conclusion was supported by our analyses of both the other disease-causing mutants and the series of C-terminal truncation constructs of alphaB-crystallin. The 450delA and 464delCT mutants could only be refolded and assayed as a complex with wild type alphaB-crystallin, which was not the case for Q151X alphaB-crystallin. From these studies, we conclude that all three disease-causing mutations (450delA, 464delCT, and Q151X) in the C-terminal extension destabilize alphaB-crystallin and increase its tendency to self-aggregate. We propose that it is this, rather than a catastrophic loss of chaperone activity, which is a major factor in the development of the reported diseases for the three disease-causing mutations studied here. In support of this hypothesis, we show that Q151X alphaB-crystallin is found mainly in the insoluble fraction of cell extracts from transient transfected cells, due to the formation of cytoplasmic aggregates.
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Affiliation(s)
- Victoria H Hayes
- School of Biological and Biomedical Sciences, South Road Science Site, Durham University, Durham DH1 3LE
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6
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Harris F, Biswas S, Singh J, Dennison S, Phoenix DA. Calpains and their multiple roles in diabetes mellitus. Ann N Y Acad Sci 2007; 1084:452-80. [PMID: 17151322 DOI: 10.1196/annals.1372.011] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Type 2 diabetes mellitus (T2DM) can lead to death without treatment and it has been predicted that the condition will affect 215 million people worldwide by 2010. T2DM is a multifactorial disorder whose precise genetic causes and biochemical defects have not been fully elucidated, but at both levels, calpains appear to play a role. Positional cloning studies mapped T2DM susceptibility to CAPN10, the gene encoding the intracellular cysteine protease, calpain 10. Further studies have shown a number of noncoding polymorphisms in CAPN10 to be functionally associated with T2DM while the identification of coding polymorphisms, suggested that mutant calpain 10 proteins may also contribute to the disease. Here we review recent studies, which in addition to the latter enzyme, have linked calpain 5, calpain 3, and its splice variants, calpain 2 and calpain 1 to T2DM-related metabolic pathways along with T2DM-associated phenotypes, such as obesity and impaired insulin secretion, and T2DM-related complications, such as epithelial dysfunction and diabetic cataract.
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Affiliation(s)
- Frederick Harris
- Department of Forensic and Investigative Science, University of Central Lancashire, Preston, PR1 2HE, United Kingdom
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Hoehenwarter W, Klose J, Jungblut PR. Eye lens proteomics. Amino Acids 2006; 30:369-89. [PMID: 16583312 DOI: 10.1007/s00726-005-0283-9] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2005] [Accepted: 09/01/2005] [Indexed: 01/12/2023]
Abstract
The eye lens is a fascinating organ as it is in essence living transparent matter. Lenticular transparency is achieved through the peculiarities of lens morphology, a semi-apoptotic process where cells elongate and loose their organelles and the precise molecular arrangement of the bulk of soluble lenticular proteins, the crystallins. The 16 crystallins ubiquitous in mammals and their modifications have been extensively characterized by 2-DE, liquid chromatography, mass spectrometry and other protein analysis techniques. The various solubility dependant fractions as well as subproteomes of lenticular morphological sections have also been explored in detail. Extensive post translational modification of the crystallins is encountered throughout the lens as a result of ageing and disease resulting in a vast number of protein species. Proteomics methodology is therefore ideal to further comprehensive understanding of this organ and the factors involved in cataractogenesis.
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Affiliation(s)
- W Hoehenwarter
- Max Planck Institute for Infection Biology, Core Facility Protein Analysis, Berlin, Germany
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8
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Neal R, Aykin-Burns N, Ercal N, Zigler JS. Pb2+ exposure alters the lens αA-crystallin protein profile in vivo and induces cataract formation in lens organ culture. Toxicology 2005; 212:1-9. [PMID: 15905016 DOI: 10.1016/j.tox.2005.03.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2004] [Revised: 03/09/2005] [Accepted: 03/16/2005] [Indexed: 10/25/2022]
Abstract
Epidemiological data supports lead exposure as a risk factor for cataract development. Previous studies which demonstrated oxidative imbalances in the lens following in vivo Pb(2+) exposure support the idea that lead exposure can alter the lens biochemical homeostasis which may ultimately lead to loss of lens clarity with time. alpha-Crystallin, a major lens structural protein and molecular chaperone, undergoes various post-translational modifications upon aging which may contribute to decreased chaperone function and contribute to loss of lens clarity. This study evaluated the impact of 5 weeks of oral Pb(2+) exposure (peripheral Pb(2+) level approximately 30 microg/dL) on the alphaA-crystallin protein profile of the lens from Fisher 344 rats. Decreases in relative protein spot intensity of more acidic forms of alphaA- and betaA(4)-crystallin and of truncated forms of alphaA-crystallin were noted. This data indicates that changes in post-translational processing of crystallins do occur in vivo following short courses of clinically relevant Pb(2+)-exposure. In addition, organ culture of lenses from 4.5-month-old rats in 5 microM Pb(2+) resulted in opacities, demonstrating that lead is toxic to the lens and can induce a loss of lens clarity.
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Affiliation(s)
- R Neal
- Laboratory of Mechanisms of Ocular Disease, National Institutes of Health, National Eye Institute, Protein Biochemistry Section, NIH Campus Building 7, Bethesda, MD 20892, USA.
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Neal RE, Bettelheim FA, Lin C, Winn KC, Garland DL, Zigler JS. Alterations in human vitreous humour following cataract extraction. Exp Eye Res 2005; 80:337-47. [PMID: 15721616 DOI: 10.1016/j.exer.2004.09.015] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2004] [Accepted: 09/24/2004] [Indexed: 10/26/2022]
Abstract
Cataract extraction is associated with the risk of posterior vitreous detachment, macular edema and retinal detachment possibly as a result of a disturbance to the vitreous body during surgery. While it is common for lens cortical fiber debris to leak into the vitreous humour during cataract extraction, the extent to which the vitreous humour is altered post-surgery is unknown. The current study examines the integrity of the vitreous humour of pseudophakic and phakic human donor eyes by comparing the proteome, the viscosity and the size distribution of macromolecules in different regions of the vitreous humour from human pseudophakic and phakic donor eyes. Major differences between the proteomes of anterior and posterior vitreous humour were observed in phakic and pseudophakic donor eyes. Seventeen spots identified as complete, modified or cleaved forms of alphaA-, alphaB-, betaA4-, betaB2, and gammaS-crystallins were present in the anterior vitreous humour of all pseudophakic eyes studied. Crystallins were not detected in the posterior vitreous humour of the pseudophakic eye or the vitreous humour of the phakic eye. Significant alterations in abundance and/or modification of transthyretin, alpha antitrypsin, and retinoic acid binding protein were observed in all locations of pseudophakic vitreous humour as compared to phakic samples. In addition, a significant decrease in the number and intensity of protein spots was observed for the posterior vitreous humour of pseudophakic eyes when compared to posterior vitreous humour of phakic eyes. Proteins which were affected include antioxidant proteins and enzymes such as carbonic anhydrase and trisephosphate isomerase. A reversal of the viscosity gradient, anterior to posterior, in the vitreous humour of pseudophakic eyes was observed concomitant with alterations in the distribution of 50 nm particles. These particles are likely primarily composed of hyaluronan. While varying degrees of vitreous degradation may have existed prior to surgery and may have contributed to the cataract formation, in no case did the phakic donor eyes exhibit the same alterations in the vitreous humour proteome, viscosity or particle sizes as did the pseudophakic donor eyes. The examination of phakic/pseudophakic donor eye pairs confirmed that the vitreous humour proteome and structural integrity were very similar in the matched phakic donor eye to eyes from donors with no history of cataract. Even though the number of samples for this study was limited, the observed changes support the hypothesis that alterations in the vitreous humour proteome occur in psuedophakic eyes with concurrent alterations in the structure of the vitreous humor. These modifications of the microenvironment of the retina may contribute to the development of retinal complications following cataract surgery.
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Affiliation(s)
- R E Neal
- National Eye Institute, National Institutes of Health, 7 Memorial Drive, MSC 0703, Bethesda, MD 20892-0703, USA.
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10
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Sinha D, Hose S, Zhang C, Neal R, Ghosh M, O'Brien TP, Sundin O, Goldberg MF, Robison WG, Russell P, Lo WK, Samuel Zigler J. A spontaneous mutation affects programmed cell death during development of the rat eye. Exp Eye Res 2005; 80:323-35. [PMID: 15721615 DOI: 10.1016/j.exer.2004.09.014] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2004] [Accepted: 09/29/2004] [Indexed: 12/30/2022]
Abstract
We have discovered a spontaneous mutation in the Sprague-Dawley rat with a novel eye phenotype that we have named Nuc1. The Nuc1 mutation behaves as a single semi-dominant locus with an intermediate phenotype in the heterozygotes. Heterozygotes exhibit nuclear cataracts. Homozygous Nuc1 rats are fully viable and have microphthalmia, retinal abnormalities and disruption of lens structure shortly before birth. The homozygous mutant shows no obvious pathology outside of the eye, indicating that the mutation is highly eye specific in its effects. An unusual feature of the mutation is that it prevents the normal programmed loss of nuclei from lens fiber cells, but does not affect the loss of other organelles. TUNEL, light, and electron microscopic studies show normal intact nuclei in lens fibers, in contrast to many other models with degenerate nuclei and unlike normal lenses where no such nuclei remain. The beaded filament protein, filensin, is down-regulated in fibers of Nuc1, while heat shock cognate 70 is up-regulated. Homozygous retinas are thicker than normal, and TUNEL labeling indicates roughly half the number of apoptotic cells compared to a wild-type retina. The transient layer of Chievitz persists in adult Nuc1 retina, indicative of delayed development. Hence, Nuc1 is a novel mutation that could be an eye-specific regulator of apoptosis.
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Affiliation(s)
- Debasish Sinha
- Department of Ophthalmology, School of Medicine, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21287, USA.
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Pountney DL, Treweek TM, Chataway T, Huang Y, Chegini F, Blumbergs PC, Raftery MJ, Gai WP. Alpha B-crystallin is a major component of glial cytoplasmic inclusions in multiple system atrophy. Neurotox Res 2005; 7:77-85. [PMID: 15639800 DOI: 10.1007/bf03033778] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Multiple system atrophy (MSA) is characterized by the formation of oligodendroglial cytoplasmic inclusions (GCIs) consisting of alpha-synuclein filaments. AlphaB-crystallin, a small chaperone protein that binds to unfolded proteins and inhibits aggregation, has been documented in GCIs. We investigated the relative abundance and speciation of alphaB-crystallin in GCIs in MSA brains. We also examined the influence of alphaB-crystallin on the formation of cytoplasmic inclusions in cultured glial cells. Immunohistochemistry and confocal microscopy revealed alphaB-crystallin is a prominent component of GCIs, more abundant than in Lewy bodies in Lewy body dementia. One- and two-dimensional gel electrophoresis and mass spectrometric analysis of GCIs immunopurified from MSA brains indicated that alphaB-crystallin is a major protein component with multiple post-translationally modified species. In cultured C6 glioma cells treated with the proteasomal inhibitor, lactacystin, to induce accumulation of ubiquitinated proteins, a subset of cells showed increased cytoplasmic staining for alphaB-crystallin. Proteasome-inhibited cells transfected with GFP-tagged alpha-synuclein resulted in ubiquitin- and alphaB-crystallin-positive aggregates resembling GCIs in MSA brains. Our results indicate that alphaB-crystallin is a major chaperone in MSA, and suggest a role of the protein in the formation of inclusion bodies in glial cells.
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Affiliation(s)
- D L Pountney
- Department of Human Physiology, Flinders University, Adelaide 5001, Australia
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12
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Abstract
There is emerging evidence to suggest that the unregulated Ca(2+)-mediated proteolysis of essential lens proteins by calpains might be a major contributor to some forms of cataract in both animals and humans. Moreover, recently solved calpain structures have revealed molecular-level details of the activation mechanism used by these proteases, enabling the structure-based design of potent calpain inhibitors with the potential to act as anti-cataract agents. These agents offer the first real hope of an urgently needed alternative to the surgical treatment of at least some forms of cataract and relief from a life-depreciating condition on a global scale.
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Affiliation(s)
- Suman Biswas
- Department of Ophthalmology, Royal Preston Hospital, Preston, PR2 9HT, UK
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13
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Ueda Y, Fukiage C, Shih M, Shearer TR, David LL. Mass measurements of C-terminally truncated alpha-crystallins from two-dimensional gels identify Lp82 as a major endopeptidase in rat lens. Mol Cell Proteomics 2002; 1:357-65. [PMID: 12118077 DOI: 10.1074/mcp.m200007-mcp200] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Molecular chaperone activity of lens alpha-crystallins is reduced by loss of the C terminus. The purpose of this experiment was to 1) determine the cleavage sites produced in vitro by ubiquitous m-calpain and lens-specific Lp82 on alpha-crystallins, 2) identify alpha-crystallin cleavage sites produced in vivo during maturation and cataract formation in rat lens, and 3) estimate the relative activities of Lp82 and m-calpain by appearance of protease-specific cleavage products in vivo. Total soluble protein from young rat lens was incubated with recombinant m-calpain or Lp82 and 2 mM Ca2+. Resulting fragmented alpha-crystallins were separated by two-dimensional gel electrophoresis. Eluted alpha-crystallin spots were analyzed by mass spectrometry. Cleavage sites on insoluble alpha-crystallins were determined similarly in mature rat lens nucleus and in cataractous rat lens nucleus induced by selenite. In vitro proteolysis of alphaA-crystallin by Lp82 and m-calpain produced unique cleavage sites by removing 5 and 11 residues, respectively, from the C terminus. In vivo, the protease-specific truncations removing 5 and 11 residues from alphaA were both found in maturing lens, whereas only the truncation removing 5 residues was found in cataractous lens. Other truncation sites, common to both calpain isoforms, resulted from the removal of 8, 10, 16, 17, and 22 residues from the C terminus of alphaA. Using uniquely truncated alphaA-crystallins as in vivo markers, Lp82 and m-calpain were both found to be active during normal maturation of rat lens, whereas Lp82 seemed especially active during selenite cataract formation. These C-terminal truncations decrease chaperone activity of alpha-crystallins, possibly leading to the observed increases in insoluble proteins during aging and cataract. The methodology that allowed accurate mass measurements of proteins eluted from 2D gels should be useful to examine rapidly other post-translational modifications.
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Affiliation(s)
- Yoji Ueda
- Department of Oral Molecular Biology and Casey Eye Institute, Oregon Health and Science University, Portland, Oregon 97201, USA
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Colvis C, Garland D. Posttranslational modification of human alphaA-crystallin: correlation with electrophoretic migration. Arch Biochem Biophys 2002; 397:319-23. [PMID: 11795889 DOI: 10.1006/abbi.2001.2669] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
alphaA-crystallin is a major protein component of the human lens. It is known to undergo posttranslational modification. This study was done to further elucidate the temporal and spatial nature of these posttranslational modifications and to correlate the modified forms with electrophoretic migration. We dissected normal human lenses into concentric shells of fiber cells, separated the proteins by two-dimensional electrophoresis, and identified modified forms by mass spectrometry. We found that alphaA-crystallin migrated as a major spot and in over 20 additional protein spots. The extent of modification correlated with the age of the fiber cells and the depth within a lens. A correlation was also seen between these parameters and the concentration of modified forms that had full-length sequences but migrated at more acidic positions. These proteins were phosphorylated, acetylated, and/or deamidated. A few proteins migrated to a more basic position than the major form of alphaA-crystallin. The locations of several species that were truncated after C-terminal residues Ser172 and Ser162 were identified. Each of these species had intact N termini. The similarity of the C-terminal cleavage sites found in alphaA- and alphaB-crystallins was noted.
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Affiliation(s)
- Christine Colvis
- Laboratory of Mechanisms of Ocular Diseases, National Eye Institute, Bethesda, Maryland 20892, USA
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15
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Poon TC, Johnson PJ. Proteome analysis and its impact on the discovery of serological tumor markers. Clin Chim Acta 2001; 313:231-9. [PMID: 11694264 DOI: 10.1016/s0009-8981(01)00677-5] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
BACKGROUND Proteomics is a rapidly growing field of research that is becoming increasingly important as we enter the post-genome era. Remarkable improvements in the technologies of high-resolution two-dimensional polyacrylamide gel electrophoresis (2D PAGE) and mass spectrometry (MS) have marked the start of proteome analysis and its application to the study of human diseases. Besides studying the proteins involved in carcinogenesis, it is also applicable to the discovery of serological tumor markers for clinical uses, such as for hepatocellular carcinoma. CONCLUSIONS The combination of 2D PAGE and MS is the most widely used technique for proteomics, although other more automated high-throughput techniques are being developed.
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Affiliation(s)
- T C Poon
- Department of Clinical Oncology, Sir Y.K. Pao Centre for Cancer, Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong, China
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