Rat lens γ-crystallinsCharacterization of the six gene products and their spatial and temporal distribution resulting from differential synthesis (original) (raw)
Related papers
2012
Background: The small heat shock proteins, ␣A-crystallin and ␣B-crystallin are considered to be two subunits of one single monolithic lens protein, ␣-crystallin. Results: ␣A-Crystallin and ␣B-crystallin fractionate independent of each other and in two separate membrane compartments. Conclusion: ␣A-Crystallin and ␣B-crystallin are two independent proteins in the lens. Significance: These data provide functional insight into why ␣A-crystallin and ␣B-crystallin null mice have disparate phenotypes.
Journal of Biological Chemistry, 2012
Background: The small heat shock proteins, ␣A-crystallin and ␣B-crystallin are considered to be two subunits of one single monolithic lens protein, ␣-crystallin. Results: ␣A-Crystallin and ␣B-crystallin fractionate independent of each other and in two separate membrane compartments. Conclusion: ␣A-Crystallin and ␣B-crystallin are two independent proteins in the lens. Significance: These data provide functional insight into why ␣A-crystallin and ␣B-crystallin null mice have disparate phenotypes.
Biochemical and Biophysical Research Communications, 1974
incorporation of ~3H3 leucine into ollgomeric a-crystallin via individual subunits has beenmeasured in epithelial cells and cortex fiber cells from adult bovine lenses in vitro. Our data show that the ratio of [3H~ leucine incorporation via subunlts aB2 and aA 2 Ts shifted from a value of about 1:2 in epithelial cells to a value of about 1:3 in fiber cells. Thus, in this system, cellular differentiation is accompanied by a change in the stolchiometry of assembly of individual subunits to form the oligomerlc a-crystallin molecule. These results indicate possible changes in the rates of synthesis of individual a-crystallln subunits. a-Crystallin is an ollgomerlc structural protein that is found in both epithelial cells and fiber cells of the bovine lens (1) and has a molecular weight of approximately 1 X 106 (2, 3). Treatment with urea and mercaptoethanol dissociates the oligomer into its polypeptide subunits, all of which have single molecular weights of about 25,000 (4). These subunits can be resolved into two acidic proteins (aA 1 and aA2) , which have isoelectric points of 5.6 and 5.9, respectively, and two basic proteins (aB 1 and aB2) , which have isoelectric points *Research sponsored by the U. S. Atomic Energy Commission under contract with the Union Carbide Corporation.
Biochemical and Biophysical Research Communications, 1970
The vertebrate lens is composed of two distinct cell types, the epithelial cell and the fiber cell. ol-Crystallin, a structural protein found in both cell types, is composed of four subunits @Ai, olA2, aB1, and olB2). In the epithelial cells the cr-crystallin consists mainly of crA2 and crB2 with trace amounts of crA1 and cyB1. In the fiber cell there is a large increase in the amount of c~A1 and olBl subunits. This quantitative increase in two specific subunits is related to the process of cellular growth and differentiation in the vertebrate lens.
Journal of Biological Chemistry, 2011
To elucidate the morphological and cellular changes due to introduction of a charge during development and the possible mechanism that underlies cataract development in humans as a consequence of an additional charge, we generated a transgenic mouse model mimicking deamidation of Asn at position 101. The mouse model expresses a human ␣A-crystallin gene in which Asn-101 was replaced with Asp, which is referred to as ␣AN101D-transgene and is considered to be "deamidated" in this study. Mice expressing ␣AN101D-transgene are referred to here CRYAA N101D mice. All of the lines showed the expression of ␣AN101D-transgene. Compared with the lenses of mice expressing wild-type (WT) ␣A-transgene (referred to as CRYAA WT mice), the lenses of CRYAA N101D mice showed (a) altered ␣A-crystallin membrane protein (aquaporin-0 (AQP0), a specific lens membrane protein) interaction, (b) extracellular spaces between outer cortical fiber cells, (c) attenuated denucleation during confocal microscopic examination, (d) disrupted normal fiber cell organization and structure during scanning electron microscopic examination, (e) distorted posterior suture lines by bright field microscopy, and (f) development of a mild anterior lens opacity in the superior cortical region during the optical coherence tomography scan analysis. Relative to lenses with WT ␣A-crystallin, the lenses containing the deamidated ␣A-crystallin also showed an aggregation of ␣A-crystallin and a higher level of water-insoluble proteins, suggesting that the morphological and cellular changes in these lenses are due to the N101D mutation. This study provides evidence for the first time that expression of deamidated ␣A-crystallin caused disruption of fiber cell structural integrity, protein aggregation, insolubilization, and mild cortical lens opacity.
Mechanism of Cataract Formation in αA-crystallin Y118D Mutation
Investigative Opthalmology & Visual Science, 2009
Purpose-The aim of this study was to elucidate the molecular mechanisms that lead to a dominant nuclear cataract in a mouse harboring the Y118D mutation in the αA-crystallin gene. Methods-The physicochemical properties of α-crystallin obtained from mouse lenses with the Y118D mutation as well as a recombinant Y118D αA-crystallin were studied using gel filtration, two-dimensional (2D) gel electrophoresis, multi-angle light scattering, circular dichroism, fluorescence, and chaperone activities. Results-Both native α-crystallin from mutant lens and recombinant αA-Y118D displayed higher molecular mass distribution than the wild-type. Circular dichroism spectra indicated changes in the secondary structures of αA-Y118D. The αA-Y118D protein prevented nonspecific protein aggregation more effectively than wild-type αA-crystallin. The gel filtration and 2D gel electrophoresis analysis showed a significant reduction of Y118D mutant protein in comparison with wild-type αA protein of heterozygous mutant lenses. Quantitative RT-PCR results confirmed a decrease in αA and αB transcripts in the homozygous mutant α A(Y118D/Y118D) lenses. Conclusions-The αA-Y118D mutant protein itself displays an increased chaperone-like activity. However, the dominant nuclear cataract is associated with a significant decrease in the amount of αA-crystallin, leading to a reduction in total chaperone capacity needed for maintaining lens transparency. Alpha-crystallin is the major protein of vertebrate eye lens, and plays a structural role in maintaining the lens transparency and proper refractive index. It is composed of two highly homologous subunits, αA and αB. 1,2 Although the molecular weight of each individual subunit is approximately 20 kDa, the α-crystallins exist as multimers, with mass ranging from ~300 to more than 1000 kDa. The size of the oligomer varies depending on the temperature, pH, and ionic strength. 3 The two subunits assemble in vivo to form heteromeric oligomers by means of subunit exchange. 4,5
Classification of Rat Lens Crystallins and Identification of Proteins Encoded by Rat Lens mRNA
European Journal of Biochemistry, 2005
Endogenous rat lens crystallins have been separated by gel filtration into four fractions, a, fiH, Br. and 7-crystallin. Elution patterns of soluble lens proteins from animals of different ages show a relative decrease of /?H and ;-crystallin during aging. Conversely the relative amounts of r and jL-crystallin are enhanced. The rat crystallin subunits from the four fractions were characterized by one-dimensional and two-dimensional gel electrophoretic techniques. From the results a classification could be derived and a nomenclature for the soluble rat lens proteins is proposed. The products synthesized by rat lens mRNAs in a heterologous cell-free system have also been characterized. Co-electrophoresis of the radioactive products synthesized de novo together with the isolated unlabeled protein fractions on two-dimensional gels shows the relation between primary gene products and their posttranslationally modified derivatives.