Phosphatidylinositol 3-kinase function is required for transforming growth factor beta-mediated epithelial to mesenchymal transition and cell migration

J Biol Chem. 2000 Nov 24;275(47):36803-10. doi: 10.1074/jbc.M005912200.

Abstract

We have studied the role of phosphatidylinositol 3-OH kinase (PI3K)-Akt signaling in transforming growth factor beta (TGFbeta)-mediated epithelial to mesenchymal transition (EMT). In NMuMG mammary epithelial cells, exogenous TGFbeta1 induced phosphorylation of Akt at Ser-473 and Akt in vitro kinase activity against GSK-3beta within 30 min. These responses were temporally correlated with delocalization of E-cadherin, ZO-1, and integrin beta(1) from cell junctions and the acquisition of spindle cell morphology. LY294002, an inhibitor of the p110 catalytic subunit of PI3K, and a dominant-negative mutant of Akt blocked the delocalization of ZO-1 induced by TGFbeta1, whereas transfection of constitutively active p110 induced loss of ZO-1 from tight junctions. In addition, LY294002 blocked TGFbeta-mediated C-terminal phosphorylation of Smad2. Consistent with these data, TGFbeta-induced p3TP-Lux and p(CAGA)(12)-Lux reporter activities were inhibited by LY294002 and transiently expressed dominant-negative p85 and Akt mutants in NMuMG and 4T1 cells. Dominant-negative RhoA inhibited TGFbeta-induced phosphorylation of Akt at Ser-473, whereas constitutively active RhoA increased the basal phosphorylation of Akt, suggesting that RhoA in involved in TGFbeta-induced EMT. Finally, LY294002 and neutralizing TGFbeta1 antibodies inhibited ligand-independent constitutively active Akt as well as basal and TGFbeta-stimulated migration in 4T1 and EMT6 breast tumor cells. Taken together, these data suggest that PI3K-Akt signaling is required for TGFbeta-induced transcriptional responses, EMT, and cell migration.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Breast Neoplasms / metabolism
  • Cell Movement*
  • DNA-Binding Proteins / metabolism
  • Enzyme Activation
  • Female
  • Humans
  • Mesoderm / metabolism
  • Phosphatidylinositol 3-Kinases / physiology*
  • Signal Transduction
  • Smad2 Protein
  • Trans-Activators / metabolism
  • Transforming Growth Factor beta / physiology*
  • Tumor Cells, Cultured
  • rho GTP-Binding Proteins / metabolism

Substances

  • DNA-Binding Proteins
  • SMAD2 protein, human
  • Smad2 Protein
  • Trans-Activators
  • Transforming Growth Factor beta
  • Phosphatidylinositol 3-Kinases
  • rho GTP-Binding Proteins