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Rooban B Nahomi, Ram H Nagaraj; The role of αB-crystallin in TGF-β2 induced epithelial to mesenchymal transition of lens epithelial cells. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1349.
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© ARVO (1962-2015); The Authors (2016-present)
Posterior capsule opacification (PCO) is a significant complication after cataract surgery. The mesenchymal transition of lens epithelial cells (EMT) is an integral part of PCO. Even though αB-crystallin is a major protein in lens epithelial cells, its role in the EMT of those cells remains unknown. Here we demonstrate an important role for αB-crystallin in TGF-β2 induced EMT of lens epithelial cells.
Bovine lens epithelial explants were treated with an siRNA for αB-crystallin for 24 h followed by treatment with TGF-β2 (20 ng/ml) for 24 to 48 h. Lens epithelial cells (LEC) from wild type and αB-crystallin knockout mouse were treated with TGF-β2 as above. The expression of the EMT markers along with cell survival signaling pathways were studied by western blotting and qPCR. Secretion of TGF-β2 from LECs in response to TGF-β2 was assessed by an ELISA. Immunoprecipitation experiments were performed to determine the binding of αB-crystallin with Snail-1.
The treatment of TGF-β2 in bovine lens explants and mouse LEC resulted in the upregulation EMT-associated proteins (α-SMA, fibronectin, Integrin β1, MMP-9 and Snail-1) and down regulation of (E-cadherin and ZO-1) at the mRNA and protein levels. We also observed an increase in the phosphorylation of p44/42 MAPK (T202/Y204), p38MAPK (T180/Y182), Akt (S473) and Smad2 (S245/250/255) when compared to untreated cells. However, prior treatment with an siRNA for αB-crystallin inhibited TGF-β2 induced effects. In the LEC from αB-crystallin knockout mice, the effects of TGF-β2 were similarly reduced. Mouse LEC treated with TGF-β2 showed secretion of TGF-β2 into the culture medium, which was significantly reduced in αB-crystallin knockout LEC. Treatment of HeLa cells (cells with low basal expression of αB-crystallin) with TGF-β2 for 48 h upregulated αB-crystallin and translocation of αB-crystallin to the nucleus along with translocation of Smad2 and Snail-1. In TGF-β2 treated cells αB-crystallin was found to be associated with Snail-1. These effects of TGF-β2 were inhibited in cells treated with an siRNA for αB-crystallin.<br />
Our data suggest that αB-crystallin plays an important role in TGF-β2 induced EMT in lens epithelial cells. αB-crystallin might be relevant in fibrosis of epithelial cells in other tissues as well.
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