Regulation of the bioavailability of thioredoxin in the lens by a specific thioredoxin-binding protein (TBP-2)

Namal P M Liyanage, M Rohan Fernando, Marjorie F. Lou

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

Thioredoxin (TRx) is known to control redox homeostasis in cells. In recent years, a specific TRx binding protein called thioredoxin binding protein-2 (TBP-2) was found in other cell types and it appeared to negatively regulate TRx bioavailability and thereby control TRx biological function. In view of the sensitivity of lens transparency to redox status, proper regulation of TRx bioavailability is of the utmost importance. This study was conducted to examine the presence and function of TBP-2 in human lens epithelial cells (HLE B3). We cloned human lens TBP-2 from a human cDNA library (GenBank accession number AY 594328) and showed that it is fully homologous to the human brain TBP-2 gene. The recombinant TBP-2 protein was partially purified and mass spectrometric analysis confirmed its sequence homology to that of brain TBP-2. Immunoprecipitates obtained from HLE B3 cells using anti-TRx and anti-TBP-2 antibodies showed the presence of TRx and TBP-2 in immunoprecipitates indicating the formation of a TRx-TBP-2 complex in vivo. Furthermore, under H2O2-stress conditions, TRx gene expression was transiently up-regulated while TBP-2 gene expression was inversely down-regulated as seen in both HLE B3 cells and in the epithelial cell layers from cultured pig lenses. Cells with overexpressed TBP-2 showed lower TRx activity, grew slower and were more susceptible to oxidative stress-induced apoptosis. This is the first report of the presence of a TRx-specific binding protein in the lens. Our data suggest that TBP-2 is likely a negative regulator for the bioavailability, and therefore, the overall function of TRx in the lens.

Original languageEnglish (US)
Pages (from-to)270-279
Number of pages10
JournalExperimental Eye Research
Volume85
Issue number2
DOIs
StatePublished - Aug 1 2007

Fingerprint

Thioredoxins
Protein Binding
Lenses
Biological Availability
Carrier Proteins
Oxidation-Reduction
human TXNIP protein
Epithelial Cells
Gene Expression
Nucleic Acid Databases
Brain
Sequence Homology
Gene Library
Oxidative Stress
Homeostasis
Swine

Keywords

  • lens epithelial cells
  • oxidative stress
  • thioredoxin
  • thioredoxin binding protein

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems

Cite this

Regulation of the bioavailability of thioredoxin in the lens by a specific thioredoxin-binding protein (TBP-2). / Liyanage, Namal P M; Fernando, M Rohan; Lou, Marjorie F.

In: Experimental Eye Research, Vol. 85, No. 2, 01.08.2007, p. 270-279.

Research output: Contribution to journalArticle

Liyanage, Namal P M ; Fernando, M Rohan ; Lou, Marjorie F. / Regulation of the bioavailability of thioredoxin in the lens by a specific thioredoxin-binding protein (TBP-2). In: Experimental Eye Research. 2007 ; Vol. 85, No. 2. pp. 270-279.
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