Lens Crystallins: The Evolution and Expression of Proteins for a Highly Specialized Tissue

Wistow, Graeme; Piatigorsky, Joram

doi:10.1146/annurev.bi.57.070188.002403

Cited by 721 publications

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“…The diverse crystallins comprise 80-90% of the soluble protein of vertebrate lenses (4)(5)(6). The ubiquitous crystallins (the ␣-and the ␤͞␥-crystallins) are represented in all vertebrate lenses whereas the taxon-specific crystallins (also called enzymecrystallins because they are identical to or derived from metabolic enzymes) are limited to selected species (4,7).…”

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“…The ubiquitous crystallins (the ␣-and the ␤͞␥-crystallins) are represented in all vertebrate lenses whereas the taxon-specific crystallins (also called enzymecrystallins because they are identical to or derived from metabolic enzymes) are limited to selected species (4,7). The two ␣-crystallins (␣A and ␣B) originated by duplication of an ancestral small heat shock protein (shsp) gene (5,6).…”

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Adaptive evolution of small heat shock protein/ αB-crystallin promoter activity of the blind subterranean mole rat,Spalax ehrenbergi

Hough

Avivi

Davis

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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Blind mole rats have degenerated subcutaneous eyes that are visually nonfunctional. In this investigation, we have compared the tissue specificity of the small heat shock protein (shsp)͞␣B-crystallin promoter of the mole rat superspecies, Spalax ehrenbergi, with that of the mouse. Earlier experiments showed that mouse shsp͞ ␣B-crystallin promoter͞enhancer activity is high in the lens and moderate in the heart and skeletal muscle of transgenic mice. Here, we show in transgenic mouse experiments using the firefly luciferase reporter gene that, despite relatively few changes in sequence, the mole rat shsp͞␣B-crystallin promoter͞enhancer has selectively lost lens activity after 13.5 days of embryogenesis (E13.5). The ratios of mole rat͞mouse promoter activity were 0.01 for lens, 1.7 for heart, and 13.6 for skeletal muscle in 8-wk-old transgenic mice. Our data indicate that the shsp͞␣B-crystallin promoter͞enhancer has undergone adaptive changes corresponding to the subterranean evolution of the blind mole rat. We speculate that selective pressures on metabolic economy may have contributed to these tissue-specific modifications of promoter͞ enhancer function during adaptation to life underground.

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confidence: 99%

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confidence: 99%

Adaptive evolution of small heat shock protein/ αB-crystallin promoter activity of the blind subterranean mole rat,Spalax ehrenbergi

Hough

Avivi

Davis

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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“…[1][2][3] Differentiation into a lens fiber cell is accompanied by changes in cell shape, the expression of crystallins and the degradation of cellular organelles. [4][5][6] Therefore, the lens fiber cells have no nuclei and organelles. The loss of nuclei and organelles is believed to ensure the transparency of the lens.…”

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confidence: 99%

“…The loss of nuclei and organelles is believed to ensure the transparency of the lens. [4][5][6] DNase II-like acid DNase (also called DNase IIb; DLAD) 7,8) is an enzyme involved in differentiation into a lens fiber cell. Recently, Nishimoto et al 9) reported that a lack of the DLAD gene caused an inability to degrade DNA during lens cell differentiation, and the accumulates of undigested DNA in the fiber cells caused nuclear cataract in DLAD gene knockout mice.…”

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confidence: 99%

Involvement of DNase II-Like Acid DNase in the Cataract Formation of the UPL Rat and the Shumiya Cataract Rat

Nagai

Takeuchi

Kamei

et al. 2006

Biological & Pharmaceutical Bulletin

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The lens, which is composed of epithelial cells on the anterior surface of the lens and fiber cells, grows with an increase in age, and the epithelial cells move towards the lens nucleus portions during the growth. In this process, the epithelial cells were developed to become fiber cells. 1-3) Differentiation into a lens fiber cell is accompanied by changes in cell shape, the expression of crystallins and the degradation of cellular organelles. [4][5][6] Therefore, the lens fiber cells have no nuclei and organelles. The loss of nuclei and organelles is believed to ensure the transparency of the lens. 4-6) DNase II-like acid DNase (also called DNase IIb; DLAD) 7,8) is an enzyme involved in differentiation into a lens fiber cell. Recently, Nishimoto et al. 9) reported that a lack of the DLAD gene caused an inability to degrade DNA during lens cell differentiation, and the accumulates of undigested DNA in the fiber cells caused nuclear cataract in DLAD gene knockout mice. However, an appropriate model animal for investigating the change of DLAD with an increase in age has not yet been introduced.The UPL rat (UPLR) is a dominant hereditary cataract model derived from the Sprague-Dawley rat, 10) with (cataractous UPLR) and without (normal UPLR) the dominant gene for cataracts. Opacification of the lenses in cataractous UPLR starts at 35-42 d of age, and the lenses of the cataractous UPLR at 50 d of age are almost entirely opaque. The cataract appearance in the adult cataractous UPLR was 100%. [10][11][12][13] On the other hand, the Shumiya cataract rat (SCR), which was established by Shumiya and Nagase, is a hereditary cataractous rat strain. 14) Lens opacity in SCR appears spontaneously in the perinuclear and nuclear portions at 77-84 d of age, and cataract appearance in adult SCR was 66.7% (cataractous SCR), 15) with the remainder having normal clear lenses (normal SCR). Previous investigations have revealed that oxidized glutathione concentrations in the lenses of cataractous UPLRs and SCRs are increased, and reduced glutathione values are decreased. 16,17) The proteolysis of some crystallins and cytoskeletal proteins was enhanced in the lenses of cataractous UPLRs and SCRs. 11,12,18,19) The calcium concentrations in the lenses of cataractous UPLRs and SCRs rise markedly with an increase in age compared with those of normal UPLRs and SCRs, and the autolytic product of calpain was also detected in the lenses of cataractous UPLRs and SCRs. 12,20) It is noteworthy that UPLRs and SCRs cataracts are not diabetic cataracts. These changes in the biological characteristics of the lenses of cataractous UPLRs and SCRs correspond to those of human cataracts. Therefore, UPLRs and SCRs should provide a useful model for studies to reveal the mechanism of cataract development.In this report, we investigated the degradation of DNA and the expression of DLAD in the lenses of UPLRs and SCRs during cataract development. MATERIALS AND METHODS AnimalsThe rats used were male normal and cataractous (late onset type) UPLRs aged 25 to 5...

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“…The largest group is that of ␣ crystallin, which is made of aggregates of two subunits ␣A and ␣B (each of them with a mass of about 20 kDa). These subunits are individual gene products exhibiting a very low rate of evolutionary change (15,16). They exist as polydisperse high molecular weight aggregates.…”

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Enthalpy and Entropy of Hydration of Bovine Crystallins

Zhao

Bettelheim

1995

Journal of Biological Chemistry

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␣, ␤, and ␥ crystallins are the major structural proteins in mammalian lenses. Their function is to provide a transparent assembly with a refractive index gradient that is capable of focusing light onto the retina (1-3). ␣ crystallins are heteropolymers with a molecular weight of about 600,000 -1,000,000 (4 -6). ␥ crystallins, on the other hand, are a family of compact monomers with a molecular weight of 20,000 having two similar globular domains (7-10). They are located mostly in the regions of the lens with the highest refractive index (11). ␤ crystallins are of intermediate size between ␣ and ␥ crystallins forming oligomers from a variety of subunits (12)(13)(14).Thus, the lens crystallins can be subdivided into heterogeneous groups on the basis of their apparent size. The largest group is that of ␣ crystallin, which is made of aggregates of two subunits ␣A and ␣B (each of them with a mass of about 20 kDa). These subunits are individual gene products exhibiting a very low rate of evolutionary change (15, 16). They exist as polydisperse high molecular weight aggregates.The ␤ crystallins are also aggregates of many subunits with extensive polydispersity (12, 13). Sequencing studies showed that bovine ␤ crystallins have three acidic (␤A2, ␤A3/A1, and ␤A4) and three basic (␤B1, ␤B2, and ␤B3) subunits with apparent mass of 23, 25, and 23 kDa and 32, 26, and 27 kDa, respectively (14). Bovine ␤ H crystallin with apparent molecular mass of 160 -200 kDa contains all the ␤ subunits in different combinations, whereas the ␤ L crystallin fraction with apparent molecular mass of 46 -70 kDa lacks ␤B1 subunits (14). The subunits form homo-and heterodimers and -oligomers. The structure of the ␤B2 homodimer have been studied extensively (17, 18). Each domain is formed from two "Greek key" motifs, and the connecting peptide is extended. The secondary structure is made of ␤ sheets (18). The dimer stability is provided by the intersubunit ␤ sheet interfaces and the C-terminal extension in ␤B2 dimerization (18) and the N-terminal extension in the ␤A3 dimerization (19).The ␥ crystallin fraction contains the monomeric ␥ crystallins (7-10) and also monomeric ␥s crystallin, which in contrast to the other ␥ crystallins is completely denatured in 8 M urea at room temperature (20). These have a mass of approximately 20 kDa. The three-dimensional structures of ␥ crystallins have been elucidated from x-ray diffraction data for ␥B (7, 10), ␥C (8), and ␥E (9) crystallins. Each is made of a two domain structure in which each domain has two Greek key motifs.These crystallins are the products of different genes, although ␤ and ␥ crystallins may have had a common ancestral gene. The various crystallin families and their individual members are differentially expressed during development (15) leading to different mixtures of crystallins along the optical axis. The particular packing of these crystallins depends on the size as well as on the interaction of the crystallins with themselves and with the aqueous surrounding. The combination of these ef...

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Lens Crystallins: The Evolution and Expression of Proteins for a Highly Specialized Tissue

Cited by 721 publications

References 0 publications

Adaptive evolution of small heat shock protein/ αB-crystallin promoter activity of the blind subterranean mole rat,Spalax ehrenbergi

Adaptive evolution of small heat shock protein/ αB-crystallin promoter activity of the blind subterranean mole rat,Spalax ehrenbergi

Involvement of DNase II-Like Acid DNase in the Cataract Formation of the UPL Rat and the Shumiya Cataract Rat

Enthalpy and Entropy of Hydration of Bovine Crystallins

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