TGF-β2-mediated pathways play a major role in the epithelial to mesenchymal transition (EMT) of lens epithelial cells (LEC) during secondary cataract formation, which is also known as posterior capsule opacification (PCO). Although αB-crystallin is a major protein in LEC, its role in the EMT remains unknown. In a human lens epithelial cell line (FHL124) TGF-β2 treatment resulted in changes in the EMT-associated proteins at the mRNA and protein levels. This was associated with nuclear localization of αB-crystallin, phosphorylated Smad2 (pSmad2) (S245/250/255), pSmad3 (S423/425), Smad4 and Snail and the binding of αB-crystallin to these transcription factors, all of which were reduced by the downregulation of αB-crystallin. Expression of the functionally defective R120G mutant of αB-crystallin reduced TGF-β2-induced EMT in lens epithelial cells of αB-crystallin knockout mice. Treatment of bovine lens epithelial explants and mouse LEC with TGF-β2 resulted in changes in the EMT-associated proteins at the mRNA and protein levels. This was accompanied by increases in phosphorylation of p44/42 MAPK (T202/Y204), p38 MAPK (T180/Y182), Akt (S473) and Smad2 when compared with untreated cells. These changes were significantly reduced in αB-crystallin depleted or knocked out LEC. The removal of the fiber cell mass from the lens of wild type mice resulted in the upregulation of EMT-associated genes in the capsule-adherent epithelial cells, which was reduced in the αB-crystallin knockout mice. Together, our data show that αB-crystallin plays a central role in the TGF-β2-induced EMT of LEC. αB-Crystallin could be targeted to prevent PCO and pathological fibrosis in other tissues.
- secondary cataract
- heat shock proteins
- transforming growth factors
- ©2016 The Author(s)
This is an Accepted Manuscript; not the final Version of Record. Archiving permitted only in line with the archiving policy of Portland Press Limited. All other rights reserved.