Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: UMLS:C0086543 (cataract)
29,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We identified a mutation in the CRYGD gene (P23S) of the gamma-crystallin gene cluster that is associated with a polymorphic congenital cataract that occurs with frequency of approximately 0.3% in a human population. To gain insight into the molecular mechanism of the pathogenesis of gamma-crystallin isoforms, we undertook an evolutionary analysis of the available mammalian and newly obtained primate sequences of the gamma-crystallin genes. The cataract-associated serine at site 23 corresponds to the ancestral state, since it was found in CRYGD of a lower primate and all the surveyed nonprimate mammals. Crystallin proteins include two structurally similar domains, and substitutions in mammalian CRYGD protein at site 23 of the first domain were always associated with substitutions in the structurally reciprocal sites 109 and 136 of the second domain. These data suggest that the cataractogenic effect of serine at site 23 in the N-terminal domain of CRYGD may be compensated indirectly by amino acid changes in a distal domain. We also found that gene conversion was a factor in the evolution of the gamma-crystallin gene cluster throughout different mammalian clades. The high rate of gene conversion observed between the functional CRYGD gene and two primate gamma-crystallin pseudogenes (CRYGEP1 and CRYGFP1) coupled with a surprising finding of apparent negative selection in primate pseudogenes suggest a deleterious impact of recently derived pseudogenes involved in gene conversion in the gamma-crystallin gene cluster.
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PMID:Conversion and compensatory evolution of the gamma-crystallin genes and identification of a cataractogenic mutation that reverses the sequence of the human CRYGD gene to an ancestral state. 1756 61

The P23T mutant of human gammaD-crystallin (HGD) is associated with cataract. We have previously investigated the solution properties of this mutant, as well as those of the closely related P23V and P23S mutants, and shown that although mutations at site 23 of HGD do not produce a significant structural change in the protein, they nevertheless profoundly alter the solubility of the protein. Remarkably, the solubility of the mutants decreases with increasing temperature, in sharp contrast to the behavior of the native protein. This inverted solubility corresponds to a strong increase in the binding energy with temperature. Here we have investigated the liquid-liquid coexistence curve and the diffusivity of the P23V mutant and find that these solution properties are unaffected by the mutation. This means that the chemical potentials in the solution phase are essentially unaltered. The apparent discrepancy between the interaction energies in the solution phase, as compared with the solid phase, is explicable in terms of highly anisotropic interprotein interactions, which are averaged out in the solution phase but are fully engaged in the solid phase.
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PMID:Altered phase diagram due to a single point mutation in human gammaD-crystallin. 1802 89

Loss of protein thiols is a key feature associated with the onset of age-related nuclear cataract (ARNC), however, little is known about the specific sites of oxidation of the crystallins. We investigated cysteine residues in ARNC lenses and compared them with age-matched normal lenses. Proteomic analysis of tryptic digests revealed ten cysteine residues in older normal lenses that showed no significant oxidation compared to foetal counterparts (Cys 170 in betaA1/3-crystallin, Cys 32 in betaA4-crystallin, Cys 79 in betaB1-crystallin, Cys 22, Cys 78/79, C153 in gammaC-crystallin and Cys 22, Cys 24 and Cys 26 in gammaS-crystallin). Although these thiols were not oxidised in normal lenses past the 6th decade, they were present largely as disulphides in the ARNC lenses. By contrast, two cysteine residues, Cys 41 in gammaC-crystallin and Cys 18 in gammaD-crystallin, were not oxidised, even in advanced ARNC lenses. These cysteines are buried deep within the protein and any unfolding associated with cataract must be insufficient to expose them to the oxidative environment present in the centre of advanced ARNC lenses. The vast majority of the loss of protein thiol observed in such lenses is due to disulphide bond formation.
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PMID:Proteomic analysis of the oxidation of cysteine residues in human age-related nuclear cataract lenses. 1876 Nov 10

The Pro23 to Thr (P23T) mutation in human gammaD-crystallin (HGD) shows several cataract phenotypes. We found earlier [A. Pande, O. Annunziata, N. Asherie, O. Ogun, G.B. Benedek, J. Pande, Decrease in protein solubility and cataract formation caused by the Pro23 to Thr mutation in human gamma D-crystallin, Biochemistry 44 (2005) 2491-2500] that the mutation dramatically lowers the solubility of P23T but the overall protein fold is maintained. Recently we observed that solutions of P23T showed liquid-liquid phase transition behavior similar to that of HGD but the liquid-protein crystal phase transition was altered, suggesting an asymmetric distribution of "sticky" patches on the protein surface [J.J. McManus, A. Lomakin, O. Ogun, A. Pande, M. Basan, J. Pande, G.B. Benedek, Altered phase diagram due to a single point mutation in human gammaD-crystallin, Proc. Natl. Acad. Sci. USA 104 (2007) 16856-16861]. Here we present high-resolution NMR studies of HGD and P23T in which we have made nearly complete backbone assignments. The data provide a structural basis for explaining the retrograde solubility of P23T by (a) identifying possible "sticky" patches on the surface of P23T and (b) highlighting their asymmetric distribution.
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PMID:NMR study of the cataract-linked P23T mutant of human gammaD-crystallin shows minor changes in hydrophobic patches that reflect its retrograde solubility. 1927 95

The Arg14 to Cys (R14C) mutation in the human gammaD-crystallin (HGD) gene has been associated with a juvenile-onset hereditary cataract. We showed previously [Pande, A., et al. (2000) Proc. Natl. Acad. Sci. U.S.A. 97, 1993-1998] that rapid oxidation of Cys14 in the mutant leads to the formation of intermolecular, disulfide-cross-linked aggregates at physiological pH. Here we present a Raman spectroscopic analysis of R14C and HGD and show that R14C forms such aggregates even at pH 4.5. The lower pH enabled us to monitor the evolution of a variety of disulfide cross-links with distinct conformations around the CC-SS-CC dihedral angles. At least three cysteine residues are involved, forming protein-protein cross-links through disulfide-exchange reactions. From the pattern of the S-S and Trp Raman bands, we infer that Cys32 is likely to be involved in the cross-linking. The data suggest that protein precipitation in the mutant may not be the direct result of disulfide cross-linking, although such cross-linking is the initiating event. Thus, our Raman data not only enhance the understanding of the reactivity of Cys14 in the R14C mutant and the mechanism of opacity, but also shed light on the mechanism of oxidative degradation during long-term storage of thiol-containing pharmaceuticals.
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PMID:The cataract-associated R14C mutant of human gamma D-crystallin shows a variety of intermolecular disulfide cross-links: a Raman spectroscopic study. 1938 45

The human eye lens is composed of fiber cells packed with crystallins up to 450 mg/ml. Human gammaD-crystallin (HgammaD-Crys) is a monomeric, two-domain protein of the lens central nucleus. Both domains of this long lived protein have double Greek key beta-sheet folds with well packed hydrophobic cores. Three mutations resulting in amino acid substitutions in the gamma-crystallin buried cores (two in the N-terminal domain (N-td) and one in the C-terminal domain (C-td)) cause early onset cataract in mice, presumably an aggregated state of the mutant crystallins. It has not been possible to identify the aggregating precursor within lens tissues. To compare in vivo cataract-forming phenotypes with in vitro unfolding and aggregation of gamma-crystallins, mouse mutant substitutions were introduced into HgammaD-Crys. The mutant proteins L5S, V75D, and I90F were expressed and purified from Escherichia coli. WT HgammaD-Crys unfolds in vitro through a three-state pathway, exhibiting an intermediate with the N-td unfolded and the C-td native-like. L5S and V75D in the N-td also displayed three-state unfolding transitions, with the first transition, unfolding of the N-td, shifted to significantly lower denaturant concentrations. I90F destabilized the C-td, shifting the overall unfolding transition to lower denaturant concentrations. During thermal denaturation, the mutant proteins exhibited lowered thermal stability compared with WT. Kinetic unfolding experiments showed that the N-tds of L5S and V75D unfolded faster than WT. I90F was globally destabilized and unfolded more rapidly. These results support models of cataract formation in which generation of partially unfolded species are precursors to the aggregated cataractous states responsible for light scattering.
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PMID:Hydrophobic core mutations associated with cataract development in mice destabilize human gammaD-crystallin. 1975 84

Primary cataracts (CAT) are characterized as any form of opacities of the eye lenses and are not accompanied by other diseases. CAT may impair vision depending on their size, location, and their state of progression. In order to investigate the cause of congenital or juvenile CAT in inbred Angolan lions kept in German zoos, we analyzed the genomic sequences of 4 crystalline genes CRYAA, CRYAB, CRYBB2, and CRYBB1. In addition, 10 CAT candidate genes (GJA3, LIM2, CRYGA, CRYGB, CRYGC, CRYGD CRYGS, BFSP2, CRYBA4, and CRYBB1) were analyzed using adjacent microsatellites. We identified 10 single nucleotide polymorphisms in the Angolan lion crystalline genes and 9 segregating microsatellites. Nonparametric and parametric linkage analyses did not reveal any linkage between one of the analyzed markers and CAT. So, we concluded that these genes can be excluded as causative for the familial primary cataract phenotype in these Angolan lions.
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PMID:Development of feline microsatellites and SNPs for evaluating primary cataract candidate genes as cause for cataract in Angolan lions (Panthera leo bleyenberghi). 2042 16

Congenital cataract is the common cause of visual disability in children. Inherited isolated (non-syndromic) cataract represents one third of cases. Currently, at least 22 specific genes associated with isolated inherited cataract have been identified: ten crystallin genes: CRYAA, CRYAB, CRYBA1/A3, CRYBA4, CRYBB1, CRYBB2, CRYBB3, CRYGC, CRYGD, CRYGS; 4 membrane protein genes: GJA3, GJA8, MIP, LIM2; three growth and transcription factor genes: PITX3, MAF, HSF4; two cytoskeletal protein gene: BSFP1, BSFP2; chromatin modifying protein-4B gene: CHMP4B, EPHA2 and NHS, it is likely that more genes remain to be discovered. Some of the genes have been studied for their function by expression in cells or/and by knock-out animal models. The increasing availability of more detailed information about their functions makes it possible to understand the pathophysiology of congenital cataracts.
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PMID:[Progress in pathogenic genes and their functions of congenital cataract]. 2045 Jun 75

The cataract-associated Pro23 to Thr (P23T) mutation in human gammaD-crystallin (HGD) has a variety of phenotypes and is geographically widespread. Therefore, there is considerable interest in understanding the molecular basis of cataract formation due to this mutation. We showed earlier [Pande, A., et al. (2005) Biochemistry 44, 2491-2500] that the probable basis of opacity in this case is the severely compromised, retrograde solubility and aggregation of P23T relative to HGD. The dramatic solubility change occurs even as the structure of the mutant protein remains essentially unchanged in vitro. We proposed that the retrograde solubility and aggregation of P23T were mediated by net hydrophobic, protein-protein interactions. On the basis of these initial findings for P23T and related mutants, and the subsequent finding that they show atypical phase behavior [McManus, J. J., et al. (2007) Proc. Natl. Acad. Sci. U.S.A. 104, 16856-16861], we concluded that the protein clusters formed in solutions of the mutant proteins were held together by net hydrophobic, anisotropic interactions. Here we show, using chemical probes, that the surface hydrophobicities of these mutants are inversely related to their solubility. Furthermore, by probing the isolated N-terminal domains of HGD and P23T directly, we find that the increase in the surface hydrophobicity of P23T is localized in the N-terminal domain. Modeling studies suggest the presence of sticky patches on the surface of the N-terminal domain that could be engaged in the formation of protein clusters via hydrophobic protein-protein interactions. This work thus provides direct evidence of the dominant role played by net hydrophobic and anisotropic protein-protein interactions in the aggregation of P23T.
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PMID:Increase in surface hydrophobicity of the cataract-associated P23T mutant of human gammaD-crystallin is responsible for its dramatically lower, retrograde solubility. 2055 8

Human gamma-crystallins are long-lived, unusually stable proteins of the eye lens exhibiting duplicated, double Greek key domains. The lens also contains high concentrations of the small heat shock chaperone alpha-crystallin, which suppresses aggregation of model substrates in vitro. Mature-onset cataract is believed to represent an aggregated state of partially unfolded and covalently damaged crystallins. Nonetheless, the lack of cell or tissue culture for anucleate lens fibers and the insoluble state of cataract proteins have made it difficult to identify the conformation of the human gamma-crystallin substrate species recognized by human alpha-crystallin. The three major human lens monomeric gamma-crystallins, gammaD, gammaC, and gammaS, all refold in vitro in the absence of chaperones, on dilution from denaturant into buffer. However, off-pathway aggregation of the partially folded intermediates competes with productive refolding. Incubation with human alphaB-crystallin chaperone during refolding suppressed the aggregation pathways of the three human gamma-crystallin proteins. The chaperone did not dissociate or refold the aggregated chains under these conditions. The alphaB-crystallin oligomers formed long-lived stable complexes with their gammaD-crystallin substrates. Using alpha-crystallin chaperone variants lacking tryptophans, we obtained fluorescence spectra of the chaperone-substrate complex. Binding of substrate gamma-crystallins with two or three of the four buried tryptophans replaced by phenylalanines showed that the bound substrate remained in a partially folded state with neither domain native-like. These in vitro results provide support for protein unfolding/protein aggregation models for cataract, with alpha-crystallin suppressing aggregation of damaged or unfolded proteins through early adulthood but becoming saturated with advancing age.
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PMID:Partially folded aggregation intermediates of human gammaD-, gammaC-, and gammaS-crystallin are recognized and bound by human alphaB-crystallin chaperone. 2062 68


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