title: αB-crystallin is essential for the TGF-β2-mediated epithelial to mesenchymal transition of lens epithelial cells.
abstract: Transforming growth factor (TGF)-β2-mediated pathways play a major role in the epithelial to mesenchymal transition (EMT) of lens epithelial cells (LECs) 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 LEC 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 down-regulation of αB-crystallin. Expression of the functionally defective R120G mutant of αB-crystallin reduced TGF-β2-induced EMT in LECs of αB-crystallin knockout (KO) 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 increase in phosphorylation of p44/42 mitogen-activated protein kinases (MAPK) (T202/Y204), p38 MAPK (T180/Y182), protein kinase B (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 fibre cell mass from the lens of wild-type (WT) mice resulted in the up-regulation of EMT-associated genes in the capsule-adherent epithelial cells, which was reduced in the αB-crystallin KO 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.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Case Western Reserve University, School of Medicine, Cleveland, OH 44106, U.S.A. Department of Ophthalmology, University of Colorado, School of Medicine, Aurora, CO 80045, U.S.A.
authors.forename: Rooban B
authors.initials: RB
authors.lastname: Nahomi
authors.affiliation: Department of Ophthalmology, University of Colorado, School of Medicine, Aurora, CO 80045, U.S.A.
authors.forename: Mina B
authors.initials: MB
authors.lastname: Pantcheva
authors.affiliation: Department of Ophthalmology and Visual Sciences, Case Western Reserve University, School of Medicine, Cleveland, OH 44106, U.S.A. Department of Ophthalmology, University of Colorado, School of Medicine, Aurora, CO 80045, U.S.A. ram.nagaraj@ucdenver.edu.
authors.forename: Ram H
authors.initials: RH
authors.lastname: Nagaraj
mesh_terms: D000818:Animals; D002417:Cattle; D002460:Cell Line; D003459:Crystallins / Q000235:genetics / Q000378:metabolism*; D004847:Epithelial Cells / Q000187:drug effects*; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects* / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D007908:Lens, Crystalline / Q000166:cytology*; D051379:Mice; D018345:Mice, Knockout; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D051899:Smad2 Protein / Q000235:genetics / Q000378:metabolism; D051900:Smad3 Protein / Q000235:genetics / Q000378:metabolism; D051901:Smad4 Protein / Q000235:genetics / Q000378:metabolism; D000071250:Snail Family Transcription Factors / Q000235:genetics / Q000378:metabolism; D053781:Transforming Growth Factor beta2 / Q000494:pharmacology*
chemical_list: D003459:Crystallins; D051899:Smad2 Protein; D051900:Smad3 Protein; D051901:Smad4 Protein; D000071250:Snail Family Transcription Factors; D053781:Transforming Growth Factor beta2
keywords: TGF-β2; epithelial to mesenchymal transition; lens epithelial cells; αB-crystallin