Taxon-specific recruitment of enzymes as major soluble proteins in the corneal epithelium of three mammals, chicken, and squid.

Cuthbertson, R. Andrew; Tomarev, S.I.; Piatigorsky, Joram

doi:10.1073/pnas.89.9.4004

Cited by 80 publications

(88 citation statements)

References 43 publications

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“…For example, the glutathione S-transferase related S-crystallins are the major proteins of both the lens and the cornea in the squid (23). The accumulation of the same crystallin in the lens and the cornea in the squid provides additional support for the idea that crystallins are important for the optical, transparent properties of both of these eye structures.…”

Section: Discussionmentioning

confidence: 85%

“…For example, ALDH3 (22,23), TKT (24), and isocitrate dehydrogenase (25) are present at considerably higher levels in the epithelial cells of mammalian corneas than would be ex- lanes 1-3), rosey barb (P. conconius) (lanes 4 -6), and tricolor shark (B. melanopterus) (lanes 7-9); 14 g of proteins were used as markers (M). Lanes 1, 4, and 7, cornea; lanes 2, 5, and 8, lens; lanes 3, 6,and 9, the rest of the eye (eye minus lens and cornea).…”

Section: Discussionmentioning

confidence: 99%

“…pected if they served strictly metabolic roles. These enzymes are negligible in the epithelial cells of the chicken cornea, which instead accumulates peptidylprolyl cis-trans-isomerase (cyclophilin) among other water-soluble proteins (23). ALDH1 and TKT are the principal water-soluble proteins of the keratocytes in the stroma of the rabbit cornea (27).…”

Section: Discussionmentioning

confidence: 99%

“…An additional similarity with the enzyme-crystallins of the lens is that the abundant proteins in the corneal epithelial cells are taxon-specific. For example, although ALDH3 is the major protein in corneal epithelial cells of most mammals, it does not accumulate in the corneas of chicken, toad, or fish (18,23,26). Stromal keratocytes of the cornea also have putative enzyme-crystallins (27).…”

mentioning

confidence: 99%

“…Furthermore, these abundant intracellular corneal proteins are often enzymes, reminiscent of the enzyme-crystallins in the lens, suggesting that they are not serving strictly metabolic roles. For example, a major protein in most mammalian corneal epithelial cells is aldehyde dehydrogenase class 3 (ALDH3), 1 which represents 20 -40% of the water-soluble protein of the bovine (20,21), rodent, and marsupial (22,23) corneal epithelial cells. Transketolase (TKT) comprises at least 10% of the water-soluble protein of the mouse corneal epithelial cells (24) and NADP ϩ -dependent isocitrate dehydrogenase comprises approximately 13% of the water-soluble proteins of the bovine corneal epithelial cells (25).…”

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confidence: 99%

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Evidence for Gelsolin as a Corneal Crystallin in Zebrafish

Kantorow

Davis

et al. 2000

Journal of Biological Chemistry

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We have shown that gelsolin is one of the most prevalent water-soluble proteins in the transparent cornea of zebrafish. There are also significant amounts of actin. In contrast to actin, gelsolin is barely detectable in other eye tissues (iris, lens, and remaining eye) of the zebrafish. Gelsolin cDNA hybridized intensely in Northern blots to RNA from the cornea but not from the lens, brain, or headless body. The deduced zebrafish gelsolin is ϳ60% identical to mammalian cytosolic gelsolin and has the characteristic six segmental repeats as well as the binding sites for actin, calcium, and phosphatidylinositides. In situ hybridization tests showed that gelsolin mRNA is concentrated in the zebrafish corneal epithelium. The zebrafish corneal epithelium stains very weakly with rhodamine-phalloidin, indicating little Factin in the cytoplasm. In contrast, the mouse corneal epithelium contains relatively little gelsolin and stains intensely with rhodamine-phalloidin, as does the zebrafish extraocular muscle. We propose, by analogy with the diverse crystallins of the eye lens and with the putative enzyme-crystallins (aldehyde dehydrogenase class 3 and other enzymes) of the mammalian cornea, that gelsolin and actin-gelsolin complexes act as watersoluble crystallins in the zebrafish cornea and contribute to its optical properties.Focused vision in the vertebrate eye depends upon light transmission through the transparent lens and cornea. The lens is an encapsulated tissue containing a layer of anterior, cuboidal epithelial cells and posterior, elongated fiber cells (1). By contrast, the transparent cornea has an anterior squamous epithelium comprising 5-7 cell layers overlying a relatively thick extracellular stroma containing ordered collagen fibers, proteoglycans, glycosaminoglycans, and keratocytes, and finally a posterior single layer of endothelial cells (2-5).The transparent and refractive properties of the eye lens depend upon the crystallins, which often differ among species in a taxon-specific fashion (6). The diverse crystallins comprise approximately 90% of the water-soluble proteins of the lens. Many lens crystallins are either closely related or identical to metabolic enzymes (the enzyme-crystallins) or stress proteins (small heat shock proteins) that are used outside of the lens for non-refractive purposes (7-9). The dual use of crystallins for metabolism and refraction has been called gene sharing (10).Because transparency of the cellular lens involves the intracellular crystallins (11-13), studies on corneal transparency have concentrated on the highly structured extracellular stroma (14, 15). However, corneal epithelial cells, like lens cells, contain unexpectedly high proportions of selected proteins (16 -19), raising the possibility that they may have structural roles related to transparency as do lens crystallins. Furthermore, these abundant intracellular corneal proteins are often enzymes, reminiscent of the enzyme-crystallins in the lens, suggesting that they are not serving strictly metabolic roles. ...

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Section: Discussionmentioning

confidence: 85%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Evidence for Gelsolin as a Corneal Crystallin in Zebrafish

Kantorow

Davis

et al. 2000

Journal of Biological Chemistry

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Differential expression of the two δ‐crystallin genes in lens and non‐lens tissues: Shift favoring δ2 expression from embryonic to adult chickens

Zelenka

Piatigorsky

1993

Developmental Dynamics

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Chicken argininosuccinate lyase (ASL)/G-crystallin, a lens enzyme-crystallin, is encoded in two linked genes (61 and 62); only the 62 polypeptide contains ASL activity. Here we have quantified 61-and $2-crystallin mRNA in the lens, cornea, neural retina, heart, and brain at different stages of embryonic development and in 1-wk-old and 1-yr-old chickens by the polymerase chain reaction using internal 61 and 62 RNA standards. The 61/S2 mRNA ratio differed for every tissue and was regulated during development. In the embryo there was more 61 than 62 mRNA in the lens (5CL100 times), cornea (5-4 times), and neural retina (2-20 times), about equal amounts of $1 and 62 mRNA in the heart, and more 62 mRNA in the brain (15 times). $1-Crystallin mRNA differentially decreased in every tissue after hatching; by contrast, the $2 mRNA remained about the same except for the lens, where it decreased 50-fold between 1 wk and 1 yr after hatching. In the 1-yr-old chicken, the 62/81 mRNA ratios were 7 in the lens, 175 in the cornea, 22 in the neural retina, 107 in the heart, and 136 in the brain, indicating that 62-crystallin is strongly favored in all adult tissues of the chicken. The excess of 61 to 62 mRNA in the embryonic lens, cornea, and neural retina is intriguing, and suggests some connection with developing transparent eye tissues. Finally, we raise the possibility that expression of both 8-crystallin genes may create tetrameric ASL isoenzymes (perhaps with different specific activities). The unexpected predominance of 62 mRNA in the 1-yr-old lens suggests that both the enzymatic and refractive functions of ASL/6-crystallin are operative and spatially separated, with the enzymatic role present in the cortical fibers and the refractive role in the center of the lens.

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Puzzle of crystallin diversity in eye lenses

Piatigorsky

1993

Developmental Dynamics

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Crystallins have evolved by various mechanisms that are associated with high expression of their genes in the eye lens. The diversity and pattern of crystallins among different species indicate that independent events have occurred at the molecular level during the evolution of the lens in different invertebrates (jellyfish, squid, and octopus) and vertebrates. Although it is possible that different crystallins are needed to fulfill the specific needs of individual species, the unexpectedly large array of proteins that function as crystallins and their abundance in the lens raise the possibility that selective pressures optimizing the function of certain transcription factors in the lens contribute to the recruitment of crystallins. 0 1993 Wiley-Liss, Inc.

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Taxon-specific recruitment of enzymes as major soluble proteins in the corneal epithelium of three mammals, chicken, and squid.

Cited by 80 publications

References 43 publications

Evidence for Gelsolin as a Corneal Crystallin in Zebrafish

Evidence for Gelsolin as a Corneal Crystallin in Zebrafish

Differential expression of the two δ‐crystallin genes in lens and non‐lens tissues: Shift favoring δ2 expression from embryonic to adult chickens

Puzzle of crystallin diversity in eye lenses

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