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Muranov KO, Poliansky NB, Borzova VA, Kleimenov SY. Refolding Increases the Chaperone-like Activity of α H-Crystallin and Reduces Its Hydrodynamic Diameter to That of α-Crystallin. Int J Mol Sci 2023; 24:13473. [PMID: 37686274 PMCID: PMC10487585 DOI: 10.3390/ijms241713473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Revised: 08/25/2023] [Accepted: 08/28/2023] [Indexed: 09/10/2023] Open
Abstract
αH-Crystallin, a high molecular weight form of α-crystallin, is one of the major proteins in the lens nucleus. This high molecular weight aggregate (HMWA) plays an important role in the pathogenesis of cataracts. We have shown that the chaperone-like activity of HMWA is 40% of that of α-crystallin from the lens cortex. Refolding with urea significantly increased-up to 260%-the chaperone-like activity of α-crystallin and slightly reduced its hydrodynamic diameter (Dh). HMWA refolding resulted in an increase in chaperone-like activity up to 120% and a significant reduction of Dh of protein particles compared with that of α-crystallin. It was shown that the chaperone-like activity of HMWA, α-crystallin, and refolded α-crystallin but not refolded HMWA was strongly correlated with the denaturation enthalpy measured with differential scanning calorimetry (DSC). The DSC data demonstrated a significant increase in the native protein portion of refolded α-crystallin in comparison with authentic α-crystallin; however, the denaturation enthalpy of refolded HMWA was significantly decreased in comparison with authentic HMWA. The authors suggested that the increase in the chaperone-like activity of both α-crystallin and HMWA could be the result of the correction of misfolded proteins during renaturation and the rearrangement of protein supramolecular structures.
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Affiliation(s)
- Konstantin O. Muranov
- Emanuel Institute of Biochemical Physics of Russian Academy of Sciences, Moscow 119334, Russia;
| | - Nicolay B. Poliansky
- Emanuel Institute of Biochemical Physics of Russian Academy of Sciences, Moscow 119334, Russia;
| | - Vera A. Borzova
- Federal Research Centre “Fundamentals of Biotechnology” of Russian Academy of Sciences, Bach Institute of Biochemistry, Moscow 119334, Russia;
| | - Sergey Y. Kleimenov
- Koltzov Institute of Developmental Biology of Russian Academy of Sciences, Moscow 119334, Russia;
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Muranov KO, Ostrovsky MA. Biochemistry of Eye Lens in the Norm and in Cataractogenesis. BIOCHEMISTRY. BIOKHIMIIA 2022; 87:106-120. [PMID: 35508906 DOI: 10.1134/s0006297922020031] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 09/30/2021] [Accepted: 09/30/2021] [Indexed: 06/14/2023]
Abstract
The absence of cellular organelles in fiber cells and very high cytoplasmic protein concentration (up to 900 mg/ml) minimize light scattering in the lens and ensure its transparency. Low oxygen concentration, powerful defense systems (antioxidants, antioxidant enzymes, chaperone-like protein alpha-crystallin, etc.) maintain lens transparency. On the other hand, the ability of crystallins to accumulate age-associated post-translational modifications, which reduce the resistance of lens proteins to oxidative stress, is an important factor contributing to the cataract formation. Here, we suggest a mechanism of cataractogenesis common for the action of different cataractogenic factors, such as age, radiation, ultraviolet light, diabetes, etc. Exposure to these factors leads to the damage and death of lens epithelium, which allows oxygen to penetrate into the lens through the gaps in the epithelial layer and cause oxidative damage to crystallins, resulting in protein denaturation, aggregation, and formation of multilamellar bodies (the main cause of lens opacification). The review discusses various approaches to the inhibition of lens opacification (cataract development), in particular, a combined use of antioxidants and compounds enhancing the chaperone-like properties of alpha-crystallin. We also discuss the paradox of high efficiency of anti-cataract drugs in laboratory settings with the lack of their clinical effect, which might be due to the late use of the drugs at the stage, when the opacification has already formed. A probable solution to this situation will be development of new diagnostic methods that will allow to predict the emergence of cataract long before the manifestation of its clinical signs and to start early preventive treatment.
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Affiliation(s)
- Konstantin O Muranov
- Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, 119334, Russia.
| | - Mikhail A Ostrovsky
- Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, 119334, Russia
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3
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In vitro hyperglycemic condition facilitated the aggregation of lysozyme via the passage through a molten globule state. Cell Biochem Biophys 2013. [PMID: 23184703 DOI: 10.1007/s12013-012-9479-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Hyperglycemic condition i.e. an increase in blood glucose concentration has been linked to bring about structural alterations in the native state of proteins. Glucose concentrations of 50 and 100 mM in vitro, which correspond to hyperglycemic condition, were tested to investigate their effect on lysozyme native structure. Incubating enzyme with 50 and 100 mM glucose for a period of 7 days, an intermediate state on day 4 and 3 was observed, respectively. The presence of intermediate state was characterized by a 22 % increase in the intrinsic fluorescence intensity with a red shift of 20 nm compared to the native state, a 5 % increase in ANS-fluorescence intensity relative to the native due to the surfacing of hydrophobic clusters and a sharp decrease in near-UV CD signal at around 284 and 291 nm. The state retains substantial native-like secondary structure. This partially unfolded intermediate state can be referred as 'molten globule', which finally tends to aggregate on day 6 and 4 with 50 and 100 mM glucose concentration, respectively, as a result of cross-linking between lysozyme molecules. The aggregates were confirmed by the presence of β-sheet structure as depicted by far-UV CD, an increase in ThT fluorescence as well as the fibrillar morphology shown by SEM. Moreover, advanced glycation end products were also accompanied as the emission peak was observed at 460 and 470 nm corresponding to the formation of pentosidine and malonaldehyde, respectively.
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Holm T, Brøgger-Jensen MR, Johnson L, Kessel L. Glutathione preservation during storage of rat lenses in optisol-GS and castor oil. PLoS One 2013; 8:e79620. [PMID: 24260265 PMCID: PMC3834120 DOI: 10.1371/journal.pone.0079620] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Accepted: 10/02/2013] [Indexed: 11/25/2022] Open
Abstract
Background Glutathione concentration in the lens decreases in aging and cataractous lenses, providing a marker for tissue condition. Experimental procedures requiring unfrozen lenses from donor banks rely on transportation in storage medium, affecting lens homeostasis and alterations in glutathione levels. The aim of the study was to examine the effects of Optisol-GS and castor oil on lens condition, determined from their ability to maintain glutathione concentrations. Methodology/Principal Findings Rat lenses were stored in the two types of storage media at varying time intervals up to 3 days. Glutathione concentration was afterwards determined in an enzymatic detection assay, specific for both reduced and oxidized forms. Lenses removed immediately after death exhibited a glutathione concentration of 4.70±0.29 mM. In vitro stored lenses in Optisol-GS lost glutathione quickly, ending with a concentration of 0.60±0.34 mM after 3 days while castor oil stored lenses exhibited a slower decline and ended at 3 times the concentration. A group of lenses were additionally stored under post mortem conditions within the host for 6 hours before its removal. Total glutathione after 6 hours was similar to that of lenses removed immediately after death, but with altered GSH and GSSG concentrations. Subsequent storage of these lenses in media showed changes similar to those in the first series of experiments, albeit to a lesser degree. Conclusions/Significance It was determined that storage in Optisol-GS resulted in a higher loss of glutathione than lenses stored in castor oil. Storage for more than 12 hours reduced glutathione to half its original concentration, and was considered unusable after 24 hours.
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Affiliation(s)
- Thomas Holm
- Department of Ophtalmology, Glostrup Hospital, University of Copenhagen, Copenhagen, Denmark
- * E-mail:
| | | | - Leif Johnson
- Department of Ophtalmology, Glostrup Hospital, University of Copenhagen, Copenhagen, Denmark
| | - Line Kessel
- Department of Ophtalmology, Glostrup Hospital, University of Copenhagen, Copenhagen, Denmark
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5
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Kannan R, Santhoshkumar P, Mooney BP, Sharma KK. The αA66-80 peptide interacts with soluble α-crystallin and induces its aggregation and precipitation: a contribution to age-related cataract formation. Biochemistry 2013; 52:3638-50. [PMID: 23631441 DOI: 10.1021/bi301662w] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Formation of protein aggregates in the aging eye lens has been shown to correlate with progressive accumulation of specific low-molecular weight (LMW) peptides derived from crystallins. Prominent among the LMW fragments is αA66-80, a peptide derived from αA-crystallin and present at higher concentrations in the water-insoluble nuclear fractions of the aging lens. The αA66-80 peptide has amyloid-like properties and preferentially insolubilizes α-crystallin from soluble lens fractions. However, the specific interactions and mechanisms by which the peptide induces α-crystallin aggregation have not been delineated. To gain insight into the mechanisms of peptide-induced aggregation, we investigated the interactions of the peptide with α-crystallin by various biochemical approaches. The peptide weakens α-crystallin chaperone ability and drastically promotes α-crystallin aggregation via the formation of insoluble peptide-protein complexes through transient intermediates. 4,4'-Dianilino-1,1'-binaphthyl-5,5'-disulfonic acid studies suggest that the peptide induces changes in the hydrophobicity of α-crystallin that could trigger the formation and growth of aggregates. The peptide-α-crystallin aggregates were found to be resistant to dissociation by high ionic strengths, whereas guanidinium hydrochloride and urea were effective dissociating agents. We conclude that the αA66-80 peptide forms a hydrophobically driven, stable complex with α-crystallin and reduces its solubility. Using isotope-labeled chemical cross-linking and mass spectrometry, we show that the peptide binds to multiple sites, including the chaperone site, the C-terminal extension, and subunit interaction sites in αB-crystallin, which may explain the antichaperone property of the peptide and the consequential age-related accumulation of aggregated proteins. Thus, the α-crystallin-derived peptide could play a role in the pathogenesis of cataract formation in the aging lens.
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Affiliation(s)
- Rama Kannan
- Department of Biochemistry, University of Missouri , Columbia, Missouri 65211, United States
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Ciocca DR, Arrigo AP, Calderwood SK. Heat shock proteins and heat shock factor 1 in carcinogenesis and tumor development: an update. Arch Toxicol 2012; 87:19-48. [PMID: 22885793 DOI: 10.1007/s00204-012-0918-z] [Citation(s) in RCA: 194] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Accepted: 07/25/2012] [Indexed: 12/20/2022]
Abstract
Heat shock proteins (HSP) are a subset of the molecular chaperones, best known for their rapid and abundant induction by stress. HSP genes are activated at the transcriptional level by heat shock transcription factor 1 (HSF1). During the progression of many types of cancer, this heat shock transcriptional regulon becomes co-opted by mechanisms that are currently unclear, although evidently triggered in the emerging tumor cell. Concerted activation of HSF1 and the accumulation of HSPs then participate in many of the traits that permit the malignant phenotype. Thus, cancers of many histologies exhibit activated HSF1 and increased HSP levels that may help to deter tumor suppression and evade therapy in the clinic. We review here the extensive work that has been carried out and is still in progress aimed at (1) understanding the oncogenic mechanisms by which HSP genes are switched on, (2) determining the roles of HSF1/HSP in malignant transformation and (3) discovering approaches to therapy based on disrupting the influence of the HSF1-controlled transcriptome in cancer.
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Affiliation(s)
- Daniel R Ciocca
- Oncology Laboratory, Institute of Experimental Medicine and Biology of Cuyo (IMBECU), Scientific and Technological Center (CCT), CONICET, 5500 Mendoza, Argentina.
| | - Andre Patrick Arrigo
- Apoptosis Cancer and Development, Cancer Research Center of Lyon (CRCL), UMR INSERM 1052-CNRS 5286, Claude Bernard University, Lyon-1, Cheney A Building, Centre Regional Léon Bérard, 28, rue Laennec 69008 LYON, France. ;
| | - Stuart K Calderwood
- Molecular and Cellular Radiation Oncology, Department of Radiation Oncology, Beth Israel Deaconess Medical Center, Boston, MA02215
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Su SP, McArthur JD, Truscott RJW, Aquilina JA. Truncation, cross-linking and interaction of crystallins and intermediate filament proteins in the aging human lens. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2011; 1814:647-56. [PMID: 21447408 DOI: 10.1016/j.bbapap.2011.03.014] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2010] [Revised: 02/14/2011] [Accepted: 03/22/2011] [Indexed: 11/30/2022]
Abstract
The optical properties of the lens are dependent upon the integrity of proteins within the fiber cells. During aging, crystallins, the major intra-cellular structural proteins of the lens, aggregate and become water-insoluble. Modifications to crystallins and the lens intermediate filaments have been implicated in this phenomenon. In this study, we examined changes to, and interactions between, human lens crystallins and intermediate filament proteins in lenses from a variety of age groups (0-86years). Among the lens-specific intermediate filament proteins, filensin was extensively cleaved in all postnatal lenses, with truncated products of various sizes being found in both the lens cortical and nuclear extracts. Phakinin was also truncated and was not detected in the lens nucleus. The third major intermediate filament protein, vimentin, remained intact in lens cortical fiber cells across the age range except for an 86year lens, where a single ~49kDa breakdown product was observed. An αB-crystallin fusion protein (maltose-binding protein-αB-crystallin) was found to readily exchange subunits with endogenous α-crystallin, and following mild heat stress, to bind to filensin, phakinin and vimentin and to several of their truncated products. Tryptic digestion of a truncated form of filensin suggested that the binding site for α-crystallin may be in the N-terminal region. The presence of significant amounts of small peptides derived from γS- and βB1-crystallins in the water-insoluble fraction of the lens indicates that these interact tightly with cytoskeletal or membrane components. Interestingly, water-soluble complexes (~40kDa) contained predominantly γS- and βB1-crystallins, suggesting that cross-linking is an alternative pathway for modified β- and γ-crystallins in the lens.
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Affiliation(s)
- Shih-Ping Su
- School of Biological Sciences, University of Wollongong, Wollongong, NSW 2522, Australia.
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8
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Attanasio F, Cataldo S, Fisichella S, Nicoletti S, Nicoletti VG, Pignataro B, Savarino A, Rizzarelli E. Protective effects of L- and D-carnosine on alpha-crystallin amyloid fibril formation: implications for cataract disease. Biochemistry 2009; 48:6522-31. [PMID: 19441807 DOI: 10.1021/bi900343n] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Mildly denaturing conditions induce bovine alpha-crystallin, the major structural lens protein, to self-assemble into fibrillar structures in vitro. The natural dipeptide l-carnosine has been shown to have potential protective and therapeutic significance in many diseases. Carnosine derivatives have been proposed as potent agents for ophthalmic therapies of senile cataracts and diabetic ocular complications. Here we report the inhibitory effect induced by the peptide (l- and d-enantiomeric form) on alpha-crystallin fibrillation and the almost complete restoration of the chaperone activity lost after denaturant and/or heat stress. Scanning force microscopy (SFM), thioflavin T, and a turbidimetry assay have been used to determine the morphology of alpha-crystallin aggregates in the presence and absence of carnosine. DSC and a near-UV CD assay evidenced that the structural precursors of amyloid fibrils are polypeptide chain segments that lack stable structural elements. Moreover, we have found a disassembling effect of carnosine on alpha-crystallin amyloid fibrils. Finally, we show the ability of carnosine to restore most of the lens transparency in organ-cultured rat lenses exposed to similar denaturing conditions that were used for the in vitro experiments.
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9
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Attanasio F, Cascio C, Fisichella S, Nicoletti VG, Pignataro B, Savarino A, Rizzarelli E. Trehalose effects on α-crystallin aggregates. Biochem Biophys Res Commun 2007; 354:899-905. [PMID: 17266925 DOI: 10.1016/j.bbrc.2007.01.061] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2006] [Accepted: 01/16/2007] [Indexed: 10/23/2022]
Abstract
alpha-Crystallin in its native state is a large, heterogeneous, low-molecular weight (LMW) aggregate that under certain conditions may progressively became part of insoluble high-molecular weight (HMW) systems. These systems are supposed to play a relevant role in eye lens opacification and vision impairment. In this paper, we report the effects of trehalose on alpha-crystallin aggregates. The role of trehalose in alpha-crystallin stress tolerance, chaperone activity and thermal stability is studied. The results show that trehalose stabilizes the alpha-crystallin native structure, inhibits alpha-crystallin aggregation, and disaggregates preformed LMW systems not affecting its chaperone activity.
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10
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Liang JJ, Liu BF. Fluorescence resonance energy transfer study of subunit exchange in human lens crystallins and congenital cataract crystallin mutants. Protein Sci 2006; 15:1619-27. [PMID: 16751613 PMCID: PMC2242568 DOI: 10.1110/ps.062216006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Lens alpha-crystallin is an oligomeric protein with a molecular mass of 500-1000 kDa and a polydispersed assembly. It consists of two types of subunits, alphaA and alphaB, each with a molecular mass of 20 kDa. The subunits also form homo-oligomers in some other tissues and in vitro. Their quaternary structures, which are dynamic and characterized by subunit exchange, have been studied by many techniques, including fluorescence resonance energy transfer (FRET) and mass spectrometry analysis. The proposed mechanism of subunit exchange has been either by dissociation/association of monomeric subunits or by rapid equilibrium between oligomers and suboligomers. To explore the nature of subunit exchange further, we performed additional FRET measurements and analyses using a fluorescent dye-labeled W9F alphaA-crystallin as the acceptor probe and Trp in other crystallins (wild-type and R116C alphaA, wild-type and R120G alphaB, wild-type and Q155* betaB2) as the donor probe and calculated the transfer efficiency, Förster distance, and average distance between two probes. The results indicate only slight decreased efficiency and increased distance between two probes for the R116C alphaA and R120G alphaB mutations despite conformational changes.
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Affiliation(s)
- Jack J Liang
- Ophthalmic Research/Surgery, Brigham and Women's Hospital, Department of Ophthalmology, Harvard Medical School, Boston, MA 02115, USA.
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11
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Fujii N, Shimmyo Y, Sakai M, Sadakane Y, Nakamura T, Morimoto Y, Kinouchi T, Goto Y, Lampi K. Age-related changes of alpha-crystallin aggregate in human lens. Amino Acids 2006; 32:87-94. [PMID: 16699822 DOI: 10.1007/s00726-006-0303-4] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2005] [Accepted: 02/16/2006] [Indexed: 11/25/2022]
Abstract
Lens alpha-crystallin, composed of two subunits alpha A- and alpha B-crystallin, forms large aggregates in the lens of the eye. The present study investigated the aggregate of human lens alpha-crystallin from elderly and young donors. Recombinant alpha A- and alpha B-crystallins in molar ratios of alpha A to alpha B at 1:1, corresponding to the aged sample, were also studied in detail. We found by ultra-centrifugation analysis that the alpha-crystallin aggregate from elderly donors was large and heterogeneous with an average sedimentation coefficient of 30 S and a range of 20-60 S at 37 degrees C. This was higher compared to the young samples that had an average sedimentation coefficient of 17 S. The sedimentation coefficients of recombinant alpha A- and alpha B-crystallins were approximately 12 S and 15 S, respectively. Even when recombinant alpha-crystallins were mixed in molar ratios equivalent to those found in vivo, similar S values as the native aged alpha-crystallin aggregates were not obtained. Changes in the self-association of alpha-crystallin aggregate were correlated to changes in chaperone activity. Alpha-crystallin from young donors, and recombinant alpha A- and alpha B-crystallin and their mixtures showed chaperone activity, which was markedly lost in samples from the aged alpha-crystallin aggregates.
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Affiliation(s)
- N Fujii
- Research Reactor Institute, Kyoto University, Kumatori, Sennan, Osaka, Japan.
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Maekawa S, Kataoka M, Uji Y, Hibasami H, Nakashima K. Spermine induces cataract and 43-kDa protein that binds spermine possibly participates in the cataract formation. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1637:70-4. [PMID: 12527409 DOI: 10.1016/s0925-4439(02)00215-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Among polyamines (putrescine, spermidine, and spermine), spermine specifically induces cataract in an organ cultured lens. Spermine uptake nearly paralleled the cataract formation. When polyamines were added to lens soluble proteins, spermine specifically induced turbidity. When lens soluble proteins were separated by gel chromatography, heavy-molecular-weight protein (HMW, high molecular form of alpha-crystallin) and proteins between betaH- and betaL-crystallin fractions reacted with spermine and aggregated. SDS-polyacrylamide gel electrophoresis of the aggregated proteins showed that 43-kDa lens protein was commonly observed in both aggregates. Spermine-affinity chromatography of the total soluble proteins showed the binding of HMW protein to the gel and the chromatogram of the second turbidity peak in the gel chromatography showed the binding of 43-kDa protein. These results indicated that 43-kDa protein, which is present as a subunit in HMW and also in free form, binds spermine and induces turbidity of lens soluble proteins and produces cataract in a cultured lens.
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Affiliation(s)
- Satoru Maekawa
- Department of Ophthalmology, Mie University School of Medicine, Edobashi 2-174, Mie 514-8507, Tsu, Japan.
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Abstract
alpha A-Crystallin high-molecular-weight (HMW) aggregates were prepared by preheating at 80-90 degrees C and studied using spectroscopic measurements. Conformational differences were suggested based on data of increased bis-ANS (4,4(')-dianilino-1,1(')-binaphthalene-5,5(')-disulfonic acid) and ThT (thioflavin T) fluorescence as well as increased far-UV and decreased near-UV circular dichroism (CD). These results indicated that HMW aggregated alpha-crystallin was more hydrophobic than the native alpha-crystallin, possibly resulting from partial unfolding of alpha-crystallin. The two cysteines in alpha A-crystallin were mostly oxidized in HMW aggregates. The effects of HMW aggregation on the dynamic structure were studied with fluorescence resonance energy transfer; subunit exchange became slower. These results strongly suggest that HMW alpha A-crystallin aggregates result from exposure of buried beta-pleated sheets and increased hydrophobic interaction.
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Affiliation(s)
- Jack J-N Liang
- Department of Ophthalmology, Center for Ophthalmic Research, Brigham and Women's Hospital, Harvard Medical School, 221 Longwood Avenue, Boston, MA 02115, USA.
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14
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Chen SJ, Sun TX, Akhtar NJ, Liang JJ. Oxidation of human lens recombinant alphaA-crystallin and cysteine-deficient mutants. J Mol Biol 2001; 305:969-76. [PMID: 11162107 DOI: 10.1006/jmbi.2000.4348] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Disulfide cross-linking, one of the results of oxidative stress, has been thought to play an important role in cataractogenesis. High molecular mass (HMM) protein aggregation also contributes to cataract development, and a prevailing speculation is that disulfide cross-linking induces HMM aggregation. However, there is no direct evidence to support this speculation. Dimerization is an effect of disulfide cross-linking but cannot explain the size of HMM aggregates observed in the lens. alphaA-crystallin has two cysteine residues (Cys131 and Cys142) and we have prepared three Cys-deficient mutants, two single mutants (C131I and C142I) and one double mutant (C131I/C142I). They were subjected to H202 oxidation in an ascorbate-FeCl(3)-EDTA-H202 system. The effects of oxidation on the mutants, including changes in aggregate size and conformation, were compared with those of the wild-type alphaA-crystallin by FPLC gel filtration, absorption, fluorescence, and circular dichroism measurements. The results indicated that other amino acid residues besides Cys, such as Trp and Tyr, were also oxidized by H202. Disulfide dimerization alone seems to play a less important role in HMM aggregation than does the secondary conformational change resulting from the combined effect of the oxidation of Trp and Tyr as well as Cys.
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Affiliation(s)
- S J Chen
- Center for Ophthalmic Research, Brigham and Women's Hospital, Boston, MA 02115, USA
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15
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Abstract
In Alzheimer's disease, beta-amyloid peptides (betaA(1-40) and betaA(1-42)) are deposited on the brain cell surfaces as neurotoxic plaques. Some reports indicate that small heat shock proteins, Hsp27 and alphaB-crystallin, colocalize in the plaques, but their functions are not known. Interaction between betaA and alphaB-crystallin must be determined in order to understand the role of alphaB-crystallin in betaA fibril formation. We used a pyrene (Pyr)-labeled betaA(1-40) in a fluorescence energy transfer experiment. Upon incubation together at 37 degrees C, energy transfer between Trp of alphaB-crystallin and Pyr of Pyr-labeled betaA was observed, indicating that betaA participated in subunit exchange of alphaB-crystallin, which promoted fibril formation.
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Affiliation(s)
- J J Liang
- Center for Ophthalmic Research, Brigham and Women's Hospital, Department of Ophthalmology, Harvard Medical School, 221 Longwood Avenue, Boston, MA 02115, USA.
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