Role of the proteasome in TGF-beta signaling in lens epithelial cells

Investigative Ophthalmology & Visual Science
Matthew R HoslerB J Wagner

Abstract

The durability of the ubiquitin proteasome pathway in the mammalian lens makes this enzyme system a potential contributor to certain cataracts and posterior capsular opacification (PCO). The present study addresses proteasome involvement in TGF-beta induced, cataract-associated gene activation in human lens cells. HLE B-3 cells were treated with TGF-beta, in combination with the proteasome inhibitors MG-132 or lactacystin. TGF-beta target gene expression was measured by semiquantitative RT-PCR. Annexin-FITC staining and flow cytometry were used to assess apoptosis levels. Western blot analyses were performed with anti-SnoN and anti-Smad2 antibodies. TGF-beta induced the expression of alpha-smooth muscle actin, fibronectin, and TGF-beta-inducible gene mRNA in HLE B-3 cells and primary cultured human lens cells from donor tissues. TGF-beta also induced a time-dependent decrease in the level of the Smad repressor SnoN. Gamma-glutamyl-cysteine synthetase (gamma-GCS) mRNA levels decreased in the presence of TGF-beta. Proteasome inhibitor cotreatment blocked the induction of alpha-SMA mRNA, the loss of SnoN protein, the decrease in gamma-GCS mRNA, and TGF-beta-induced apoptosis. The HLE B-3 cell line and primary cultured human lens c...Continue Reading

Citations

Jan 12, 2007·Molecular Biology of the Cell·George WuYong Wan
Dec 19, 2012·Human Genomics·Konstantinos Sousounis, Panagiotis A Tsonis
Sep 25, 2008·Molecular Aspects of Medicine·Christopher C FranklinTerrance J Kavanagh

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