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

Biochim Biophys Acta. 2010 Dec;1803(12):1386-95. doi: 10.1016/j.bbamcr.2010.09.001. Epub 2010 Sep 15.

Abstract

The Jagged/Notch pathway has been implicated in TGFβ1 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 TGFβ1-stimulated gene responses in human kidney epithelial cells in vitro. TGFβ1 treatment of HK-2 and RPTEC cells for 24h increased Jagged1 (a Notch ligand) and Hes1 (a Notch target) mRNA. This response was inhibited by co-incubation with Compound E, an inhibitor of γ-secretase (GSI), an enzyme required for Notch receptor cleavage and transcription regulation. In both cell types, TGFβ1-responsive genes associated with epithelial-mesenchymal transition such as E-cadherin and vimentin were also affected by γ-secretase inhibition, but other TGFβ1 targets such as connective tissue growth factor (CTGF) and thrombospondin-1 (THBS1) were not. TGFβ1-induced changes in Jagged1 expression preceded EMT-associated gene changes, and co-incubation with GSI altered TGFβ1-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 TGFβ1, but did not affect α-smooth muscle actin expression, suggesting differential requirements for Notch signalling within the TGFβ1-responsive gene subset. Increased Jagged1 expression upon TGFβ1 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 TGFβ1-responsive genes, and that complex signalling pathways are involved in the crosstalk between TGFβ1 and Notch cascades in kidney epithelia.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calcium-Binding Proteins / metabolism*
  • Cell Line
  • Epithelial Cells / metabolism
  • Humans
  • Intercellular Signaling Peptides and Proteins / metabolism*
  • Jagged-1 Protein
  • Kidney / cytology
  • Kidney / metabolism*
  • Membrane Proteins / metabolism*
  • Microscopy, Fluorescence
  • Polymerase Chain Reaction
  • Receptors, Notch / metabolism*
  • Serrate-Jagged Proteins
  • Signal Transduction*
  • Transforming Growth Factor beta1 / metabolism*

Substances

  • Calcium-Binding Proteins
  • Intercellular Signaling Peptides and Proteins
  • JAG1 protein, human
  • Jagged-1 Protein
  • Membrane Proteins
  • Receptors, Notch
  • Serrate-Jagged Proteins
  • Transforming Growth Factor beta1