Identification of a cytosolic NADP+-dependent isocitrate dehydrogenase that is preferentially expressed in bovine corneal epithelium. A corneal epithelial crystallin

Lijie Sun, Tung Tien Sun, Robert M. Lavker*

*Corresponding author for this work

Research output: Contribution to journalArticle

56 Scopus citations

Abstract

Recently, metabolic enzymes have been observed in both the lens and corneal epithelium at levels greatly exceeding what is necessary for normal metabolic functions. These proteins have been termed taxon-specific crystallins and are thought to play a role in maintaining tissue transparency. We report here that cytosolic NADP+-dependent isocitrate dehydrogenase (ICDH) represents a new corneal crystallin. Using suppression subtractive hybridization, we identified a gene (with a deduced amino acid sequence that showed 94% identity to rat cytosolic NADP+-dependent ICDH) that is preferentially expressed in bovine corneal epithelium. Northern blots established that its mRNA level in the corneal epithelium was 31-, 39-, 133- , 230-, and 929-fold more than in the liver, bladder epithelium, stomach epithelium, brain, and heart, respectively. This mRNA was detected primarily in corneal epithelial basal cells by in situ hybridization. SDS- polyacrylamide gel electrophoresis, two-dimensional gel analysis, and Western blotting showed that this protein was overexpressed in the corneal epithelium, constituting ~13% of the total soluble bovine corneal epithelial proteins. Enzyme assays showed a corresponding overabundance of this protein in bovine corneal epithelium. Taken together, these data indicate that bovine cytosolic ICDH fulfills the criteria for a corneal epithelial crystallin and may be involved in maintaining corneal epithelial transparency.

Original languageEnglish (US)
Pages (from-to)17334-17341
Number of pages8
JournalJournal of Biological Chemistry
Volume274
Issue number24
DOIs
StatePublished - Jun 11 1999

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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