RON Receptor Tyrosine Kinase Regulates Epithelial Mesenchymal Transition and the Expression of Pro-Fibrotic Markers via Src/Smad Signaling in HK-2 and NRK49F Cells

Abstract

Receptor tyrosine kinases (RTKs) play important roles in the pathogenic processes of kidney fibrosis. However, the pathophysiological roles of recepteur d’origine nantais (RON), one of the receptor tyrosine kinases, have not yet been defined. We investigated whether the activation or sequence-specific small interfering RNA (siRNA) suppression of RON could regulate epithelial mesenchymal transition (EMT) and the expression of pro-fibrotic markers, and its underlying molecular mechanisms. Stable cell lines and transient transfection for RON and the transfected cells of siRNA for RON were developed to investigate the molecular mechanisms in human kidney proximal tubular epithelial (HK-2) and interstitial fibroblasts (NRK49F) cells. RON overexpression induced EMT and increased expression of fibrosis-related proteins such as N-cadherin, vimentin, transforming growth factor-β (TGFβ), αSMA, and fibronectin in HK-2 and NRK49F cells. RON overexpression increased various RTKs and the phosphorylation of Src (Y416) and Smad, while inhibition of RON by siRNA attenuated the expression of EMT- and fibrosis-related proteins and decreased RTKs such as insulin-like growth factor receptor (IGFR), fibroblast growth factor receptor 1 (FGFR1), vascular endothelial growth factor receptor (VEGFR), and platelet-derived growth factor receptor (PDGFR), as well as the phosphorylation of Src and Smad pathways. siRNA silencing of Src also attenuated the expression of IGFR, FGFR1, VEGFR, and PDGFR. Inhibition of RON can exert an anti-fibrotic effect by the inhibition of EMT and other RTKs through control of Src and Smad pathways in HK-2 and NRK49F cells.

Role of SIK1 in the transition of acute kidney injury into chronic kidney disease

“…Multiple intracellular signal transduction pathways are involved in the expression and activation of EMT and renal fibrosis, including TGF-β signaling pathway, PI3K/AKT pathway, Src pathway, MAPK pathway, and WNT signaling pathway [36][37][38][39][40][41]. Among these, WNT/ β-catenin signaling pathway, the most classic WNT pathway, was widely studied.…”

TGF-β1 Signaling: Immune Dynamics of Chronic Kidney Diseases

“…Thus, EMT contributes to the pathogenesis of kidney fibrosis via direct generation of the collagens producing myofibroblasts ( 62 ). In the canonical pathway, Smad3 is highly activated in the UUO kidney in vivo , and TGF-β1 treated renal tubular epithelial cells in vitro , driving EMT for the myofibroblast generation and associated kidney fibrosis, which is blocked by Smad3 deletion and TGF-β1 neutralizing antibody ( 63 – 65 ). Non-canonical pathways, including MAPK, Rho-like GTPase, PI3K/Akt, and Wnt signaling, have been illustrated to have played emerging roles in EMT induction ( 28 , 66 , 67 ).…”

Integrin-α9β1 as a Novel Therapeutic Target for Refractory Diseases: Recent Progress and Insights

“…While α9β1 binding to TNC supports phenotypic and functional alterations to EMT, with increases in N-cadherin, α-SMA, vimentin and snail (mesenchymal markers), as well as a decrease in E-cadherin [epithelial marker; ( 64 )]. The above process is accompanied by phosphorylation of β-catenin through the Src signaling pathway, which has been proved to be closely associated with EMT ( 70 , 71 ). In addition, fibronectin-EDA also imparts the EMT phenotype through integrin-α9β1 ( 39 ), and irigenin (a novel lead from the Western Himalayan chemiome that can be isolated from the rhizomes of Belamcanda chinensis ) has an anti-metastasis capacity by selectively blocking the α9β1 and α4β1 integrin binding sites with the C-C loop of EDA ( 92 ).…”