Purchase this article with an account.
VijayKrishna Raghunathan, Brad W Rose, Sara M Thomasy, Paul Russell, Christopher J Murphy; Distinct roles of YAP/TAZ in myofibroblast transformation. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5144.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Corneal wound healing is a complex process wherein corneal re-epithelialization and keratocyte-fibroblast-myofibroblast (KFM) transformation play critical roles. KFM transformation is critical to wound healing with dysregulation of this process lead to corneal opacification. Yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ), mediators of the Hippo pathway, function as co-activators of transcription and interact with the TGFβ pathway via SMADs. Their effects are largely influenced by their phosphorylation state that in turn dictates their subcellular localization. The purpose of this study was to determine the distinct roles of YAP/TAZ in TGFβ1 mediated myofibroblast transformation.
Primary and immortalized (hTERT) human corneal fibroblasts (HCFs) were used for this study. Cells were transfected with control siRNA or siRNA specific to YAP and TAZ for 48 h and cultured in the presence or absence of 2.5 ng/ml TGFβ1 for up to 72 h. RNA was isolated and quantitative PCR was performed to determine mRNA expression of α-smooth muscle actin (αSMA, a myofibroblast phenotype marker), CTGF and YAP/TAZ. Expression / knockdown of proteins were confirmed by Western blotting.
Within 24 h, treatment of control fibroblasts with 2.5 ng/ml TGFβ1 resulted in nuclear translocation of YAP and was associated with a significant reduction in phosphorylated-YAP. Following TAZ knockdown, αSMA expression was significantly elevated (3-fold) but was unaltered following YAP knockdown when compared with control siRNA treated HCFs (without TGFβ1 treatment). However, treatment of TAZ knockdown cells with 2.5ng/ml TGFβ1 resulted in a dramatic increase (24-fold) in αSMA expression in comparison with YAP knockdown cells (7.5-fold) or control siRNA (8.2-fold) cells.
Nuclear localization of YAP facilitates activation of TGFβ1 mediated myofibroblast transformation. Results from the siRNA studies indicate that YAP and TAZ may play differential roles in KFM transformation and that TAZ may promote maintenance of the fibroblast phenotype. We speculate that modulating YAP/TAZ function offers a promising avenue for development of therapeutics for the treatment of dysregulated corneal wound healing.
This PDF is available to Subscribers Only