Activation of the pro-survival phosphatidylinositol 3-kinase/AKT pathway by transforming growth factor-beta1 in mesenchymal cells is mediated by p38 MAPK-dependent induction of an autocrine growth factor.
Transforming growth factor-beta1 (TGF-beta1) is a multifunctional cytokine involved in differentiation, growth, and survival of mesenchymal cells while inhibiting growth/survival of most other cell types. The mechanism(s) of pro-survival signaling by TGF-beta1 in mesenchymal cells is unclear. In this report, we demonstrate that TGF-beta1 protects against serum deprivation-induced apoptosis of mesenchymal cells isolated from patients with acute lung injury and of normal human fetal lung fibroblasts (IMR-90). TGF-beta receptor(s)-activated signaling in these cells involves rapid activation of the Smad and p38 MAPK pathways within minutes of TGF-beta1 treatment followed by a more delayed activation of the pro-survival phosphatidylinositol 3-kinase-protein kinase B (PKB)/Akt pathway. Pharmacological inhibition of p38 MAPK with SB203580 or expression of a p38 kinase-deficient mutant protein inhibits TGF-beta1-induced PKB/Akt phosphorylation. Conditioned medium from TGF-beta1-treated cells rapidly induces PKB/Akt activation in an SB203580- and suramin-sensitive manner, suggesting p38 MAPK-dependent production of a secreted growth factor that activates this pro-survival pathway by an autocrine/paracrine mechanism. Inhibition of the phosphatidylinositol 3-kinase-PKB/Akt pathway blocks TGF-beta1-induced resistance to apoptosis. These results demonstrate the activation of a novel TGF-beta1-activated pro-survival/anti-apoptotic signaling pathway in mesenchymal cells/fibroblasts that may explain cell-specific actions of TGF-beta1 and provide mechanistic insights into its pro-fibrotic and tumor-promoting effects.
Horowitz
Jeffrey C
JC
Department of Medicine, University of Michigan Medical Center, Ann Arbor, Michigan 48109, USA.
Lee
Daniel Y
DY
Waghray
Meghna
M
Keshamouni
Venkateshwar G
VG
Thomas
Peedikayil E
PE
Zhang
Hengmin
H
Cui
Zongbin
Z
Thannickal
Victor J
VJ
D017209:Apoptosis; D015153:Blotting, Western; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002455:Cell Division; D002470:Cell Survival; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000494:pharmacology; D016207:Cytokines / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000378:metabolism; D003720:Densitometry; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D005347:Fibroblasts / Q000378:metabolism; D006133:Growth Substances / Q000378:metabolism; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D008168:Lung / Q000473:pathology; D008648:Mesoderm / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008954:Models, Biological; D009154:Mutation; D010641:Phenotype; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D053773:Transforming Growth Factor beta1; D053781:Transforming Growth Factor beta2; D048051:p38 Mitogen-Activated Protein Kinases
D017077:Culture Media, Conditioned; D016207:Cytokines; D004277:DNA, Single-Stranded; D004791:Enzyme Inhibitors; D006133:Growth Substances; D007093:Imidazoles; D011725:Pyridines; C508960:TGFB1 protein, human; C509041:TGFB2 protein, human; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D053781:Transforming Growth Factor beta2; D019869:Phosphatidylinositol 3-Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; C093642:SB 203580