Jagged/Notch signalling is required for a subset of TGFβ1 responses in human kidney epithelial cells

The Jagged/Notch pathway has been implicated in TGF beta 1 responses in epithelial cells in diabetic nephropathy and other fibrotic conditions in vivo. Here, we identify that Jagged/Notch signalling is required for a subset of TGF beta 1-stimulated gene responses in human kidney epithelial cells in vitro. TGF beta 1 treatment of HK-2 and RFTEC cells for 24 h increased Jagged1 (a Notch ligand) and Hes1 (a Notch target) mRNA. This response was inhibited by co-incubation with Compound E, an inhibitor of gamma-secretase (GSI), an enzyme required for Notch receptor cleavage and transcription regulation. In both cell types, TGF beta 1-responsive genes associated with epithelial-mesenchymal transition such as E-cadherin and vimentin were also affected by gamma-secretase inhibition, but other TGF beta 1 targets such as connective tissue growth factor (CTGF) and thrombospondin-1 (THBS1) were not. TGF beta 1-induced changes in Jagged] expression preceded EMT-associated gene changes, and co-incubation with GSI altered TGF beta 1-induced changes in cell shape and cytoskeleton. Transfection of cells with the activated, cleaved form of Notch (NICD) triggered decreased expression of E-cadherin in the absence of TGF beta 1, but did not affect a-smooth muscle actin expression, suggesting differential requirements for Notch signalling within the TGF beta 1-responsive gene subset. Increased Jagged1 expression upon TGF beta 1 exposure required Smad3 signalling, and was also regulated by PI3K and ERK. These data suggest that Jagged/Notch signalling is required for a subset of TGF beta 1-responsive genes, and that complex signalling pathways are involved in the crosstalk between TGF beta 1 and Notch cascades in kidney epithelia. (C) 2010 Elsevier B.V. All rights reserved.