Role for integrin-linked kinase in mediating tubular epithelial to mesenchymal transition and renal interstitial fibrogenesis
Yingjian Li, … , Chuanyue Wu, Youhua Liu
Yingjian Li, … , Chuanyue Wu, Youhua Liu
Published August 15, 2003
Citation Information: J Clin Invest. 2003;112(4):503-516. https://doi.org/10.1172/JCI17913.
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Article Nephrology

Role for integrin-linked kinase in mediating tubular epithelial to mesenchymal transition and renal interstitial fibrogenesis

Abstract

Under pathologic conditions, renal tubular epithelial cells can undergo epithelial to mesenchymal transition (EMT), a phenotypic conversion that is believed to play a critical role in renal interstitial fibrogenesis. However, the underlying mechanism that governs this process remains largely unknown. Here we demonstrate that integrin-linked kinase (ILK) plays an important role in mediating tubular EMT induced by TGF-β1. TGF-β1 induced ILK expression in renal tubular epithelial cells in a time- and dose-dependent manner, which was dependent on intracellular Smad signaling. Forced expression of ILK in human kidney proximal tubular epithelial cells suppressed E-cadherin expression and induced fibronectin expression and its extracellular assembly. ILK also induced MMP-2 expression and promoted cell migration and invasion in Matrigel. Conversely, ectopic expression of a dominant-negative, kinase-dead form of ILK largely abrogated TGF-β1–initiated tubular cell phenotypic conversion. In vivo, ILK was markedly induced in renal tubular epithelia in mouse models of chronic renal diseases, and such induction was spatially and temporally correlated with tubular EMT. Moreover, inhibition of ILK expression by HGF was associated with blockade of tubular EMT and attenuation of renal fibrosis. These findings suggest that ILK is a critical mediator for tubular EMT and likely plays a crucial role in the pathogenesis of chronic renal fibrosis.

Authors

Yingjian Li, Junwei Yang, Chunsun Dai, Chuanyue Wu, Youhua Liu

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ILK induction by TGF-β1 in renal epithelial cells is dependent on Smad s...
ILK induction by TGF-β1 in renal epithelial cells is dependent on Smad signaling. (a–c) Pharmacological inhibition of different signal transduction pathways does not affect ILK induction by TGF-β1. HKC cells were pretreated with either various chemical inhibitors or vehicle (DMSO) for 30 minutes, followed by incubating in the absence or presence of 2 ng/ml TGF-β1 for 0.25, 0.5, 1 hour, 3 hours (a and b) and for 24 hours (c), respectively. Specific inhibitors for PI3K (10 nM wortmannin), Mek1 (10 μM PD98059), p38 MAPK (20 μM SC68376), PKA (0.3 μM PKA inhibitor [PKAI]), and PKC (50 nM Ro-31-8220) were used, respectively. Cell lysates were immunoblotted with Ab’s against phosphospecific Akt (p-Akt) and total Akt (a), phosphospecific and total p38 MAPK (p-p38 and p38, respectively) (b), ILK, and actin (c), respectively. (d–f) Overexpression of inhibitory Smad-7 abolishes ILK induction by TGF-β1. A stable cell line overexpressing inhibitory Smad-7 (HKCSmad7) was established by transfection of Smad-7 expression vector. A cell line with mock transfection of empty pcDNA3 vector (HKCpcDNA3) was used as control. Cells were treated with 2 ng/ml of TGF-β1 for various periods of time as indicated. (d) Cell lysates were blotted with phosphospecific (p-Smad2) and total Smad-2, respectively. (e) Cell lysates were blotted with Ab’s against ILK, Smad-7, and actin, respectively. (f) Graphical presentation of relative ILK abundance normalized to actin following TGF-β1 treatment in HKCpcDNA3 and HKCSmad7 cells. AU, arbitrary units.