Purchase this article with an account.
Frank J. Lovicu, Leila Mahmutovic, Magdalena Wojciechowski, Lucy J. Dawes, John W. McAvoy; MAPK/ERK1/2 Signaling In Tgfß-induced Lens Epithelial To Mesenchymal Transition (EMT). Invest. Ophthalmol. Vis. Sci. 2012;53(14):1061.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Aberrant changes in lens epithelial cell behavior, leading to an epithelial-to-mesenchymal transition (EMT), are characteristic of many forms of human cataract. This EMT has been reported to be mediated through transforming growth factor β (TGF-β)-signaling. Recent studies by our laboratory have shown that the loss of a negative regulator of MAPK/ERK1/2 signaling, Sprouty (Spry), specifically in the lens, results in aberrant TGFß-signaling and subsequent EMT and cataract. Based on this, we hypothesise that ERK1/2-signaling plays a role in TGFß-induced EMT and cataract.
Rat lens epithelial explants were treated with TGFß to induce EMT in the presence or absence of UO126 (MAPKK/MEK1 inhibitor). Cells in lens epithelial explants were assessed for their ability to undergo an EMT, assaying for phenotypic changes, together with EMT markers, including alpha-smooth muscle actin (α-sma) accumulation. TGFß’s ability to induce ERK1/2 phosphorylation under these conditions was also examined using western blotting.
TGFß directly induced the phosphorylation of ERK1/2 in lens epithelial explants. Blocking TGFß-induced ERK1/2 activation with UO126 resulted in suppression of different features of TGFß-induced EMT, primarily preventing lens epithelial cells acquiring a myofibroblastic phenotype, accompanied by increased cell survival and a reduction in the incidence of lens capsule contraction. Consistent with this, the expression of α-sma was also shown to be dependent on ERK1/2 signaling.
ERK1/2-signaling is involved in different aspects of TGFß-mediated EMT in lens epithelial explants. We propose that the maintenance of normal cellular processes in the lens, and hence lens transparency, is achieved by tight regulation of receptor-mediated signaling (including the Ras-ERK/MAPK pathway) by negative regulators, such as Spry. Further studies will be directed at determining the exact interplay between the ERK1/2 and canonical Smad pathways leading to TGFß-mediated EMT and cataract and how these pathways are in turn regulated.
This PDF is available to Subscribers Only