Phosphatidylinositol 3-kinase function is required for transforming growth factor beta-mediated epithelial to mesenchymal transition and cell migration.
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.
Bakin
A V
AV
Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
Tomlinson
A K
AK
Bhowmick
N A
NA
Moses
H L
HL
Arteaga
C L
CL
D001943:Breast Neoplasms / Q000378:metabolism; D002465:Cell Movement; D004268:DNA-Binding Proteins / Q000378:metabolism; D004789:Enzyme Activation; D005260:Female; D006801:Humans; D008648:Mesoderm / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D015398:Signal Transduction; D051899:Smad2 Protein; D015534:Trans-Activators / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000502:physiology*; D014407:Tumor Cells, Cultured; D020741:rho GTP-Binding Proteins / Q000378:metabolism
D004268:DNA-Binding Proteins; C497782:SMAD2 protein, human; D051899:Smad2 Protein; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D019869:Phosphatidylinositol 3-Kinases; D020741:rho GTP-Binding Proteins